JP6621570B2 - Lithographic printing plate precursor and lithographic printing plate preparation method - Google Patents

Description

  The present disclosure relates to a lithographic printing plate precursor and a method for producing a lithographic printing plate.

In general, a lithographic printing plate comprises an oleophilic image area that receives ink in the printing process and a hydrophilic non-image area that receives dampening water. Lithographic printing utilizes the property that water and oil-based inks repel each other, so that the oleophilic image area of the lithographic printing plate is the ink receiving area and the hydrophilic non-image area is dampened with the water receiving area (ink non-receiving area). As described above, a difference in ink adhesion is caused on the surface of a lithographic printing plate, and after ink is applied only to an image portion, the ink is transferred to a printing medium such as paper and printed.
In order to produce this lithographic printing plate, a lithographic printing plate precursor (PS plate) in which an oleophilic photosensitive resin layer (image recording layer) is provided on a hydrophilic support has been widely used. Usually, the lithographic printing plate precursor is exposed through an original image such as a lithographic film, and then the portion that becomes the image portion of the image recording layer is left, and the other unnecessary image recording layer is made an alkaline developer or organic A lithographic printing plate is obtained by performing plate making by a method of dissolving and removing with a solvent and exposing a hydrophilic support surface to form a non-image portion.

In addition, due to growing interest in the global environment, environmental issues related to waste liquids associated with wet processing such as development processing have been highlighted.
For the above environmental problems, simplification and no processing of development or plate making are directed. As one simple manufacturing method, a method called “on-press development” is performed. That is, after the exposure of the lithographic printing plate precursor, conventional development is not performed, but it is mounted on a printing machine as it is, and unnecessary portions of the image recording layer are removed at the initial stage of a normal printing process.
Examples of conventional lithographic printing plate precursors include those described in US Patent Application Publication No. 2009/0047599 or US Patent Application Publication No. 2013/0052582.

In the planographic printing plate, a planographic printing plate excellent in the number of printable plates (hereinafter also referred to as “printing durability”) is required.
As a result of intensive studies, the present inventors have found that the lithographic printing plate precursor described in US Patent Application Publication No. 2009/0047599 or US Patent Application Publication No. 2013/0052582 is a lithographic printing plate to be obtained. It has been found that there is a problem that the printing durability of the ink is insufficient and the color of the exposed part is also insufficient.

The problem to be solved by the embodiments of the present invention is to provide a lithographic printing plate precursor having excellent printing durability and a lithographic printing plate precursor having excellent color development.
The problem to be solved by another embodiment of the present invention is to provide a method for preparing a lithographic printing plate using the lithographic printing plate precursor.

Means for solving the above problems include the following aspects.
<1> It has an image recording layer on a hydrophilic support, and the image recording layer contains a polymerization initiator, an infrared absorber, a polymerizable compound, and an acid color former, and the infrared absorber has the following formula: A lithographic printing plate precursor comprising a compound represented by 1.

R ₁ and R ₂ each independently represents a hydrogen atom or an alkyl group, R ₁ and R ₂ may be linked to each other to form a ring, and R _{3 to} R ₆ are each independently a hydrogen atom or an alkyl group. R ₇ and R ₈ each independently represents an alkyl group or an aryl group, Y ₁ and Y ₂ each independently represent an oxygen atom, a sulfur atom, —NR ₀ — or a dialkylmethylene group, Ar ₁ and Ar ₂ each independently represent a group which forms a benzene ring or a naphthalene ring which may have -X described later, and A ₁ represents -NR ₉ R ₁₀ , -X ₁ -L ₁ or described later. represents -X to each R ₉ and R ₁₀ are independently an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, X ₁ is an oxygen atom or a sulfur atom, L ₁ represents a hydrocarbon , Heteroaryl group, or represents a bond cleaves group of X ₁ by the heat or infrared exposure, Za represents a counter ion for neutralizing the electric charge, at least one of Ar ₁ and Ar _2, by the following formula 2 Having the group represented.
-X Formula 2
X is a halogen atom, —C (═O) —X ₂ —R ₁₁ , —C (═O) —NR ₁₂ R ₁₃ , —O—C (═O) —R ₁₄ , —CN, —SO ₂ NR ₁₅ R ₁₆ or a perfluoroalkyl group, X ₂ represents a single bond or an oxygen atom, R ₁₁ and R ₁₄ each independently represents an alkyl group or an aryl group, R ₁₂ , R ₁₃ , R ₁₅ and R ₁₆ each independently represents a hydrogen atom, an alkyl group or an aryl group.

<2> The lithographic printing plate precursor as described in <1> above, wherein in the formula 1, only one of Ar ₁ and Ar ₂ has a group represented by the formula 2.
<3> The lithographic printing plate precursor as described in <1> or <2> above, wherein X in the formula 2 is a fluorine atom, a chlorine atom or —C (═O) OR ₁₇ .
R ₁₇ represents an alkyl group or an aryl group.
<4> The lithographic printing plate precursor as described in <2> or <3> above, wherein in the formula 1, A ₁ is —NR ₁₈ R ₁₉ or —S—R ₂₀ .
R ₁₈ and R ₁₉ each independently represents an aryl group, and R ₂₀ represents a hydrocarbon group or a heteroaryl group.
<5> Any one of the above <1> to <4>, wherein the difference between the HOMO of the compound represented by Formula 1 and the HOMO of at least one of the polymerization initiators is 0.60 eV or less. The lithographic printing plate precursor described in 1.
<6> The lithographic printing plate precursor as described in any one of <1> to <5>, wherein the polymerization initiator is a borate compound.
<7> The lithographic printing plate precursor as described in <6>, wherein the borate compound is a tetraarylborate compound or a monoalkyltriarylborate compound.
<8> The lithographic printing plate precursor as described in any one of <1> to <7>, wherein the polymerization initiator includes an electron donating polymerization initiator and an electron accepting polymerization initiator.
<9> Any of the above <1> to <8>, wherein the acid color former is at least one compound selected from the group consisting of a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound. The lithographic printing plate precursor as described in one.
<10> The lithographic printing plate precursor as described in any one of <1> to <9>, wherein Za is an organic anion containing a carbon atom.
<11> The lithographic printing plate precursor as described in any one of <1> to <10>, wherein Za is a sulfonimide anion.
<12> The step of exposing the lithographic printing plate precursor according to any one of the above <1> to <11> imagewise to form an exposed portion and an unexposed portion; and
A method for preparing a lithographic printing plate comprising a step of supplying at least one of printing ink and fountain solution to remove the unexposed portion.

According to the embodiment of the present invention, a lithographic printing plate having excellent printing durability can be obtained, and a lithographic printing plate precursor having excellent color development can be provided.
According to another embodiment of the present invention, a method for producing a lithographic printing plate using the lithographic printing plate precursor can be provided.

Hereinafter, the contents of the present disclosure will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.
In addition, in this specification, "-" which shows a numerical range is used by the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.
Moreover, in the description of groups (atomic groups) in this specification, the description that does not indicate substitution and non-substitution includes those that have a substituent as well as those that do not have a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In this specification, “(meth) acryl” is a term used in a concept including both acryl and methacryl, and “(meth) acryloyl” is a term used as a concept including both acryloyl and methacryloyl. It is.
In addition, the term “process” in this specification is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term is used as long as the intended purpose of the process is achieved. included. In the present disclosure, “mass%” and “weight%” are synonymous, and “part by mass” and “part by weight” are synonymous.
Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.
In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) in the present disclosure use columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) unless otherwise specified. The molecular weight was detected by a gel permeation chromatography (GPC) analyzer using a solvent THF (tetrahydrofuran) and a differential refractometer and converted using polystyrene as a standard substance.
In the present specification, the term “lithographic printing plate precursor” includes not only a lithographic printing plate precursor but also a discarded plate precursor. Further, the term “lithographic printing plate” includes not only a lithographic printing plate prepared by subjecting a lithographic printing plate precursor to operations such as exposure and development, but also a discarded plate. In the case of a discarded original plate, exposure and development operations are not necessarily required. The discarded plate is a lithographic printing plate precursor to be attached to a plate cylinder that is not used when, for example, printing a part of paper in single color or two colors in color newspaper printing.
Hereinafter, the present disclosure will be described in detail.

(Lithographic printing plate precursor)
The lithographic printing plate precursor according to the present disclosure has an image recording layer on a hydrophilic support, and the image recording layer contains a polymerization initiator, an infrared absorber, a polymerizable compound, and an acid color former, An infrared absorber contains the compound represented by following formula 1.
Moreover, the lithographic printing plate precursor according to the present disclosure can be suitably used as a lithographic printing plate precursor for on-press development.

R ₁ and R ₂ each independently represents a hydrogen atom or an alkyl group, R ₁ and R ₂ may be linked to each other to form a ring, and R _{3 to} R ₆ are each independently a hydrogen atom or an alkyl group. R ₇ and R ₈ each independently represents an alkyl group or an aryl group, Y ₁ and Y ₂ each independently represent an oxygen atom, a sulfur atom, —NR ₀ — or a dialkylmethylene group, Ar ₁ and Ar ₂ each independently represent a group which forms a benzene ring or a naphthalene ring which may have -X described later, and A ₁ represents -NR ₉ R ₁₀ , -X ₁ -L ₁ or described later. represents -X to each R ₉ and R ₁₀ are independently an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, X ₁ is an oxygen atom or a sulfur atom, L ₁ represents a hydrocarbon , Heteroaryl group, or represents a bond cleaves group of X ₁ by the heat or infrared exposure, Za represents a counter ion for neutralizing the electric charge, at least one of Ar ₁ and Ar _2, by the following formula 2 Having the group represented.
-X Formula 2
X is a halogen atom, —C (═O) —X ₂ —R ₁₁ , —C (═O) —NR ₁₂ R ₁₃ , —O—C (═O) —R ₁₄ , —CN, —SO ₂ NR ₁₅ R ₁₆ or a perfluoroalkyl group, X ₂ represents a single bond or an oxygen atom, R ₁₁ and R ₁₄ each independently represents an alkyl group or an aryl group, R ₁₂ , R ₁₃ , R ₁₅ and R ₁₆ each independently represents a hydrogen atom, an alkyl group or an aryl group.

As described above, the present inventors have a problem that conventional lithographic printing plate precursors have insufficient printing durability of the obtained lithographic printing plate and insufficient color development at exposed portions. I found out.
In addition, in order to accelerate the decomposition of the acid color former, when using an infrared absorber having an acid group, not only is the printing durability inferior, but the acid color former is also partially decomposed in the unexposed part, The present inventors have found that partial color development has occurred before, the color difference after exposure is small, and the color developability is also poor.

As a result of intensive studies by the present inventors, it has been found that a lithographic printing plate having excellent printing durability can be obtained by adopting the above configuration, and a lithographic printing plate precursor having excellent color development can be provided.
Although the detailed mechanism by which the above effect is obtained is unknown, it is presumed as follows.
Since the compound represented by Formula 1 has a specific electron-withdrawing group -X that is not an acid group at a specific position, the compound represented by Formula 1 is compared with a compound that does not have -X at a specific position. It is estimated that the HOMO (maximum occupied orbital) of the compound is lowered, and the difference between the HOMO of the compound represented by the above formula 1 and the HOMO of at least one of the polymerization initiators is reduced. .
A compound represented by the above formula 1 from the polymerization initiator at the time of exposure by using a compound represented by the above formula 1 having a specific electron withdrawing group -X at a specific position and a polymerization initiator. It is presumed that the exposure decomposition rate of the acid color former is improved and the color developability is excellent, because the electron transfer occurs and the decomposition of the polymerization initiator causes an acid or the like. Furthermore, when the polymerization initiator contains an electron donating polymerization initiator and an electron accepting polymerization initiator, and contains a compound represented by the above formula 1, a polymerizable compound, and an acid color former, printing durability is further improved. Is estimated to improve.

<Image recording layer>
A lithographic printing plate precursor according to the present disclosure has an image recording layer containing a polymerization initiator, an infrared absorber, a polymerizable compound, and an acid color former, and the infrared absorber is a compound represented by the following formula 1. including.
The image recording layer used in the present disclosure is preferably a negative image recording layer, and more preferably a water-soluble or water-dispersible negative image recording layer.
In the lithographic printing plate precursor according to the present disclosure, it is preferable that the unexposed portion of the image recording layer can be removed with at least one of dampening water and printing ink from the viewpoint of on-press developability.
Details of each component included in the image recording layer will be described below.

-Compound represented by Formula 1-
The image recording layer in the lithographic printing plate precursor according to the present disclosure contains an infrared absorber, and the infrared absorber contains a compound represented by Formula 1 above.
The infrared absorber has a function of converting the absorbed infrared light into heat and a function of exciting at least one of electron transfer and energy transfer to the polymerization initiator described later. The infrared absorbent used in the present disclosure is preferably a dye having an absorption maximum at a wavelength of 750 nm to 1,400 nm.

Ar ₁ and Ar ₂ each independently represent a group that forms a benzene ring or a naphthalene ring. The benzene ring and naphthalene ring may have a substituent other than -X. Examples of the substituent include alkyl groups, alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, carboxy groups, carboxylate groups, sulfo groups, sulfonate groups, and combinations of these. A group is preferred.
Further, in Formula 1, at least one of Ar ₁ and Ar ₂ has the group represented by Formula 2 above, and the printing durability, color developability, and the coating solution used for forming the image recording layer over time From the viewpoint of storage stability (stability over time), it is preferable that only _one of Ar ₁ and Ar ₂ has a group represented by Formula 2 above.

X in Formula 2 is a halogen atom, —C (═O) —X ₂ —R ₁₁ , —C (═O) —NR ₁₂ R ₁₃ , —O—C (═O) —R ₁₄ , —CN, — SO ₂ NR ₁₅ R ₁₆ , or a perfluoroalkyl group, from the viewpoints of printing durability, color developability and stability over time, a halogen atom, —C (═O) —X ₂ —R ₁₁ , —C (= O) —NR ₁₂ R ₁₃ , —O—C (═O) —R ₁₄ , CN, or —SO ₂ NR ₁₅ R ₁₆ is preferred, and a halogen atom, —C (═O) —O—R ₁₁ , —C (═O) —NR ₁₂ R ₁₃ , or —O—C (═O) —R ₁₄ , preferably a halogen atom, —C (═O) —O—R ₁₁ , or more preferably _{-O-C (= O) -R} 14, fluorine atom, chlorine atom, or, -C (= O) O It is particularly preferred is _17.

X ₂ represents a single bond or an oxygen atom, and is preferably an oxygen atom.
R ₁₁ and R ₁₄ each independently represent an alkyl group or an aryl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. More preferably.
R ₁₂ , R ₁₃ , R ₁₅ and R ₁₆ each independently represent a hydrogen atom, an alkyl group or an aryl group, and are a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms. Are preferable, a hydrogen atom or an alkyl group having 1 to 12 carbon atoms is more preferable, and an alkyl group having 1 to 12 carbon atoms is still more preferable.
R ₁₇ represents an alkyl group or an aryl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms.

A ₁ represents -NR ₉ R ₁₀ , -X ₁ -L ₁ or -X, and is -NR ₉ R ₁₀ or -X ₁ -L ₁ from the viewpoints of printing durability, color developability, and stability over time. It is preferable that it is -NR < ₁₈ > R < ₁₉ >, -S-R < ₂₀ >.
R ₉ and R ₁₀ each independently represents an alkyl group, an aryl group, an alkoxycarbonyl group or an arylsulfonyl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, It is more preferable that it is a C1-C12 alkyl group.
X ₁ represents an oxygen atom or a sulfur atom, L ₁ is a hydrocarbon group or a heteroaryl group is preferably a sulfur atom, the coupling of L ₁ is the X ₁ by the heat or infrared exposure cleaved It is preferably a group.
L ₁ represents a hydrocarbon group, a heteroaryl group, or a group whose bond with X ₁ is cleaved by thermal or infrared exposure, and is preferably a hydrocarbon group or a heteroaryl group from the viewpoint of printing durability. Or a heteroaryl group is more preferable, and a heteroaryl group is still more preferable.
In addition, L ₁ is preferably a group in which the bond with X ₁ is cleaved by heat or infrared exposure from the viewpoint of color developability and color fading suppression over time.
A group whose bond to X ₁ is cleaved by heat or infrared exposure will be described later.
R ₁₈ and R ₁₉ each independently represents an aryl group, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group.
R ₂₀ represents a hydrocarbon group or a heteroaryl group, preferably an aryl group or a heteroaryl group, and more preferably a heteroaryl group.

Preferred examples of the heteroaryl group for L ₁ and R ₂₀ include the following groups.

The alkyl group in R _{1 to} R ₁₀ and R ₀ is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and still more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched or a ring structure.
Specifically, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, hexadecyl group, octadecyl group Group, eicosyl group, isopropyl group, isobutyl group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl Group and 2-norbornyl group.
Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is particularly preferable.

  The alkyl group may have a substituent. Examples of substituents include alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, halogen atoms, carboxy groups, carboxylate groups, sulfo groups, sulfonate groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, and Examples include a combination of these.

The aryl group in R ₉ , R ₁₀ , R ₁₈ , R ₁₉ and R ₀ is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and an aryl group having 6 to 12 carbon atoms. Groups are more preferred.
The aryl group may have a substituent. Examples of substituents include alkyl groups, alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, halogen atoms, carboxy groups, carboxylate groups, sulfo groups, sulfonate groups, alkyloxycarbonyl groups, aryloxycarbonyl groups. And a combination of these.
Specific examples of the aryl group include phenyl, naphthyl, p-tolyl, p-chlorophenyl, p-fluorophenyl, p-methoxyphenyl, p-dimethylaminophenyl, and p-methylthio. A phenyl group, p-phenylthiophenyl group, etc. are mentioned.
Of these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, and a naphthyl group are preferable.

R ₁ and R ₂ are preferably connected to form a ring.
When R ₁ and R ₂ are linked to form a ring, the preferred number of ring members is preferably a 5- or 6-membered ring, more preferably a 6-membered ring. Also, by connecting R ₁ and R ₂ ring is preferably have an ethylenically unsaturated bond is also substituted hydrocarbon ring.

Y ₁ and Y ₂ each independently represent an oxygen atom, a sulfur atom, —NR ₀ — or a dialkylmethylene group, preferably —NR ₀ — or a dialkylmethylene group, and more preferably a dialkylmethylene group.
R ₀ represents a hydrogen atom, an alkyl group or an aryl group, and is preferably an alkyl group.

R ₇ and R ₈ are preferably the same group.
R ₇ and R ₈ are each independently preferably a linear alkyl group or an alkyl group having a sulfonate group at the terminal, more preferably a methyl group, an ethyl group or a butyl group having a sulfonate group at the terminal. preferable.
The counter cation of the sulfonate group may be a cation on a nitrogen atom in Formula 1, or may be an alkali metal cation or an alkaline earth metal cation.
Furthermore, from the viewpoint of making the compound represented by Formula 1 water-soluble, R ₇ and R ₈ are each independently preferably an alkyl group having an anion structure, and an alkyl group having a carboxylate group or a sulfonate group. More preferably, it is an alkyl group in which a sulfonate group is poured at the terminal.
Further, the maximum absorption wavelength of the compound represented by Formula 1 is lengthened, and R ₇ and R ₈ are each independently an alkyl group having an aromatic ring from the viewpoint of color developability and printing durability in a lithographic printing plate. It is preferable that it is an alkyl group having an aromatic ring at the end, and it is a 2-phenylethyl group, a 2-naphthalenylethyl group, or a 2- (9-anthracenyl) ethyl group. Particularly preferred.

R _{3 to} R ₆ each independently represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom.

Za represents a counter ion that neutralizes the charge, and when an anion species is indicated, sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, perchlorate ion, sulfonamide anion, sulfonimide anion Etc. In the case of indicating a cationic species, alkali metal ions, alkaline earth metal ions, ammonium ions, pyridinium ions or sulfonium ions are preferable, sodium ions, potassium ions, ammonium ions, pyridinium ions or sulfonium ions are more preferable, sodium ions, potassium ions Ions or ammonium ions are more preferred, and sodium ions, potassium ions or trialkylammonium ions are particularly preferred.
Among these, Za is preferably an organic anion containing a carbon atom, more preferably a sulfonate ion, a carboxylate ion, a sulfonamide anion or a sulfonimide anion from the viewpoint of printing durability and color development. An anion or a sulfonimide anion is more preferable, and a sulfonimide anion is particularly preferable.
R _{1 to} R ₈ , R ₀ , A ₁ , Ar ₁ , Ar ₂ , Y ₁ and Y ₂ may have an anion structure or a cation structure, and R _{1 to} R ₈ , R ₀ , A ₁ , If Ar ₁ , Ar ₂ , Y ₁ and Y ₂ are all neutral groups, Za is a monovalent counter anion. For example, R _{1 to} R ₈ , R ₀ , A ₁ , When Ar ₁ , Ar ₂ , Y ₁ and Y ₂ have two or more anion structures, Za can also be a counter cation.
In Formula 1, if the portion other than Za is neutral in terms of charge, Za may not be present.

As the sulfonamide anion, an arylsulfonamide anion is preferable.
Moreover, as a sulfonimide anion, a bisaryl sulfonimide anion is preferable.
Specific examples of the sulfonamide anion or the sulfonimide anion are shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

The group whose bond to X ₁ is cleaved by heat or infrared exposure is preferably a group represented by any one of the following formulas 1-1 to 1-7 from the viewpoint of color developability. A group represented by any one of -1 to Formula 1-3 is more preferable.

In Formula 1-1 to Formula 1-7, ● represents a bonding site with X _{1 in} Formula 1, and each R ¹⁰ independently represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, —OR ¹⁴ , -NR < ¹⁵ > R < ¹⁶ > or -SR < ¹⁷ >, R < ¹¹ > represents a hydrogen atom, an alkyl group, or an aryl group each independently, R < ¹² > is an aryl group, -OR < ¹⁴ >, -NR < ¹⁵ > R < ¹⁶ >,-SR < ¹⁷ >, -C ⁽⁼ O) R 18, represents an -OC (= ^{O) R 18,} or halogen ^{atom, R 13} is an aryl group, an alkenyl group, an alkoxy group or an onium ^group, in each of R 14 ^{to R 17} independently, Represents a hydrogen atom, an alkyl group or an aryl group, each of R ¹⁸ independently represents an alkyl group, an aryl group, —OR ¹⁴ , —NR ¹⁵ R ¹⁶ or —SR ¹⁷ , and Z ¹ represents a counter ion that neutralizes charges. The It is.

A preferred embodiment of the case R ^{10, R 11} and ^R 14 ^{to R 18} is an alkyl group ^are the same as the preferred embodiment of the alkyl group in R 2 to R ⁹ and ^{R 0.}
The carbon number of the alkenyl group in R ¹⁰ and R ¹³ is preferably 1-30, more preferably 1-15, and still more preferably 1-10.
A preferred embodiment in which R ^{10 to} R ¹⁸ are aryl groups is the same as the preferred embodiment of the aryl group in R ⁰ .

From the viewpoint of color development, R ¹⁰ in Formula 1-1 is preferably an alkyl group, an alkenyl group, an aryl group, —OR ¹⁴ , —NR ¹⁵ R ¹⁶ or —SR ¹⁷ , and an alkyl group, —OR ¹⁴ , It is more preferably —NR ¹⁵ R ¹⁶ or —SR ¹⁷ , further preferably an alkyl group or —OR ¹⁴ , and particularly preferably —OR ¹⁴ .
When R ¹⁰ in Formula 1-1 is an alkyl group, the alkyl group is preferably an alkyl group having an arylthio group or an alkyloxycarbonyl group at the α-position.
When R ¹⁰ in Formula 1-1 is —OR ¹⁴ , R ¹⁴ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, and an isopropyl group or a t-butyl group. More preferably, it is particularly preferably a t-butyl group.

From the viewpoint of color developability, R ¹¹ in Formula 1-2 is preferably a hydrogen atom.
From the viewpoint of color developability, R ¹² in Formula 1-2 is preferably —C (═O) OR ¹⁴ , —OC (═O) OR ¹⁴ or a halogen atom, and —C (═O) OR. ¹⁴ or —OC (═O) OR ¹⁴ is more preferable. When R ¹² in Formula 1-2 is —C (═O) OR ¹⁴ or —OC (═O) OR ¹⁴ , R ¹⁴ is preferably an alkyl group.

From the viewpoint of color developability, each R ¹¹ in Formula 1-3 is preferably independently a hydrogen atom or an alkyl group, and more preferably at least one R ¹¹ in Formula 1-3 is an alkyl group. preferable.
Moreover, the alkyl group in R ¹¹ is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 3 to 10 carbon atoms.
Furthermore, the alkyl group in R ¹¹ is preferably a branched alkyl group or a cycloalkyl group, more preferably a secondary or tertiary alkyl group or a cycloalkyl group, and an isopropyl group. , Cyclopentyl group, cyclohexyl group, or t-butyl group is more preferable.
From the viewpoint of color development, R ¹³ in Formula 1-3 is preferably an aryl group, an alkoxy group or an onium group, more preferably a p-dimethylaminophenyl group or a pyridinium group, and a pyridinium group. More preferably it is.
Examples of the onium group for R ¹³ include a pyridinium group, an ammonium group, and a sulfonium group. The onium group may have a substituent. Examples of the substituent include alkyl groups, alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, halogen atoms, carboxy groups, sulfo groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, and combinations of these. However, an alkyl group, an aryl group, and a group obtained by combining these are preferable.
Among these, a pyridinium group is preferable, and an N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N- (alkoxypolyalkyleneoxyalkyl) -3-pyridinium group, and an N-alkoxycarbonylmethyl-3-pyridinium group. N-alkyl-4-pyridinium group, N-benzyl-4-pyridinium group, N- (alkoxypolyalkyleneoxyalkyl) -4-pyridinium group, N-alkoxycarbonylmethyl-4-pyridinium group, or N-alkyl -3,5-dimethyl-4-pyridinium group is more preferable, N-alkyl-3-pyridinium group or N-alkyl-4-pyridinium group is more preferable, N-methyl-3-pyridinium group, N-octyl -3-pyridinium group, N-methyl-4-pyridinium group Or, particularly preferably N- octyl-4-pyridinium group, N- octyl-3-pyridinium group or, N- octyl-4-pyridinium group is most preferred.
When R ¹³ is a pyridinium group, examples of the counter anion include sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, p-toluenesulfonate ion, perchlorate ion, and the like. -Toluene sulfonate ions or hexafluorophosphate ions are preferred.

From the viewpoint of color developability, R ¹⁰ in Formula 1-4 is preferably an alkyl group or an aryl group, more preferably one of two R ¹⁰ is an alkyl group and the other is an aryl group.
From the viewpoint of coloring property, R ¹⁰ in Formula 1-5 is preferably an alkyl group or an aryl group, more preferably an aryl group, and still more preferably a p-methylphenyl group.
From the viewpoint of color development, each R ¹⁰ in Formula 1-6 is preferably independently an alkyl group or an aryl group, and more preferably a methyl group or a phenyl group.
From the viewpoint of color developability, Z ¹ in Formula 1-7 may be a counter ion that neutralizes charge, and may be contained in Za as a whole compound.
Z ¹ is preferably sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, p-toluenesulfonate ion or perchlorate ion, and p-toluenesulfonate ion or hexafluoro More preferably, it is a phosphate ion.

Further, the group whose bond with X ₁ is cleaved by the above-described heat or infrared exposure is particularly preferably a group represented by Formula 1-8.

In Formula 1-8, ● represents a binding site with X _{1 in} Formula 1, R ¹⁹ and R ²⁰ each independently represent an alkyl group, and Za ′ represents a counter ion that neutralizes charge. .

The bonding position between the pyridinium ring in Formula 1-8 and the hydrocarbon group containing R ²⁰ is preferably the 3-position or 4-position of the pyridinium ring, and more preferably the 4-position of the pyridinium ring.
The alkyl group in R ¹⁹ and R ²⁰ may be linear, branched or a ring structure.
The alkyl group may have a substituent, and preferred examples of the substituent include an alkoxy group and a terminal alkoxy polyalkyleneoxy group.
R ¹⁹ is preferably an alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, and further a linear alkyl group having 1 to 8 carbon atoms. A methyl group or an n-octyl group is particularly preferable.
R ²⁰ is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 8 carbon atoms, still more preferably an isopropyl group or a t-butyl group, and an isopropyl group It is particularly preferred that
Za ′ may be any counter ion that neutralizes charge, and may be contained in Za as a whole compound.
Za ′ is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and a p-toluenesulfonate ion or hexafluoro More preferably, it is a phosphate ion.

  Specific examples of the compound represented by the formula 1 include mother nucleus structures A-1 to A-54, counter anions B-1 to B-10, and counter cations C-1 to C-3. The invention is not limited to this. Specific examples of the compound represented by Formula 1 include mother nucleus structures A-1 to A-9, A-11 to A-20 and A-22 to A-54, and counter anions B-1 to B-. 10 and a compound obtained by combining one each of the mother nucleus structures A-10 and A-21 and the counter cations C-1 to C-3.

  The method for producing the compound represented by Formula 1 is not particularly limited, and can be produced by referring to a known method for producing a cyanine dye. Moreover, the method described in International Publication No. 2016/027886 can also be suitably used.

The difference (ΔE) between the HOMO of the compound infrared absorber represented by the above formula 1 and the HOMO of at least one of the polymerization initiators described later is 0.60 eV or less from the viewpoint of printing durability and color developability. Preferably, it is 0.30 eV or more and 0.60 eV or less, more preferably 0.40 eV or more and 0.58 eV or less, and particularly preferably 0.45 eV or more and 0.57 eV or less.
In addition, the difference (ΔE) between the HOMO of the compound infrared absorber represented by the above formula 1 and the HOMO of the electron donating polymerization initiator is 0.60 eV or less from the viewpoint of printing durability and color developability. Preferably, it is 0.30 eV or more and 0.60 eV or less, more preferably 0.40 eV or more and 0.58 eV or less, and particularly preferably 0.45 eV or more and 0.57 eV or less.

The calculation method of HOMO of a compound in the present disclosure is performed by the following method.
First, the counter anion in the compound to be calculated is ignored.
The structure optimization is performed by DFT (B3LYP / 6-31G (d)) using quantum chemical calculation software Gaussian09.
The MO (molecular orbital) energy calculation is performed by DFT (B3LYP / 6-31 + G (d, p) / CPCM (solvent = methanol)) with the structure obtained by the above structure optimization.
The MO energy Epre (unit: hartree) obtained by the MO energy calculation is converted into Eaft (unit: eV) used as a HOMO value in the present disclosure by the following formula.
Eaft = 0.823168 × 27.2114 × Epre−1.07634
Note that 27.2114 is simply a coefficient for converting hartree to eV, and 0.823168 and -1.07634 are adjustment coefficients so that the calculation of the HOMO of the compound to be calculated matches the actually measured value. Decided.
ΔE is determined from the difference between the HOMO of the compound represented by Formula 1 and the HOMO of a polymerization initiator such as a borate compound. In many cases, the HOMO of the compound represented by Formula 1 is larger than the HOMO of the polymerization initiator, and ΔE = HOMO of the compound represented by Formula 1—HOMO of the polymerization initiator.

As for the compound represented by Formula 1, only 1 type may be used and 2 or more types may be used together. Moreover, you may use together a pigment and dye as an infrared absorber.
The content of the infrared absorber in the image recording layer is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 5.0% by mass with respect to the total mass of the image recording layer. preferable.
The content of the compound represented by Formula 1 in the image recording layer is preferably 0.1% by mass to 10.0% by mass, and preferably 0.5% by mass to 5% with respect to the total mass of the image recording layer. 0.0 mass% is more preferable.

-Other infrared absorbers-
The image recording layer may contain an infrared absorber other than the compound represented by Formula 1 above.
Other infrared absorbers include pigments and dyes other than the compound represented by Formula 1 above.
As dyes used as other infrared absorbers, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes Is mentioned.
Particularly preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further, cyanine dyes and indolenine cyanine dyes can be mentioned. Among these, cyanine dyes are particularly preferable.

Specific examples of the cyanine dye include compounds described in paragraphs 0017 to 0019 of JP2001-133969, paragraphs 0016 to 0021 of JP2002-023360, paragraphs 0012 to 0037 of JP2002040406. The compounds described in JP-A-2002-278057, paragraphs 0034 to 0041, JP-A-2008-195018, paragraphs 0080 to 0086, particularly preferably JP-A-2007-90850, paragraph 0035 To 0043 and the compounds described in paragraphs 0105 to 0113 of JP2012-206495A.
Further, compounds described in paragraphs 0008 to 0009 of JP-A-5-5005 and paragraphs 0022 to 0025 of JP-A-2001-222101 can also be preferably used.
As the pigment, compounds described in paragraphs 0072 to 0076 of JP-A-2008-195018 are preferable.

Other infrared absorbers may be used alone or in combination of two or more. Moreover, you may use together a pigment and dye as an infrared absorber.
The content of the other infrared absorber in the image recording layer is preferably less than the content of the compound represented by the above formula 1, and is 50% by mass or less of the content of the compound represented by the above formula 1. More preferably, it is more preferably 20% by mass or less of the content of the compound represented by Formula 1 above.

-Polymerization initiator-
The image recording layer contains a polymerization initiator.
The polymerization initiator used in the present disclosure is a compound that generates polymerization initiation species such as radicals and cations by energy of light, heat, or both, and has a known thermal polymerization initiator and a bond with a small bond dissociation energy. A compound, a photopolymerization initiator and the like can be appropriately selected and used.
From the viewpoint of promoting electron transfer to the compound represented by the above formula 1 having a specific electron-withdrawing group -X at a specific position and improving printing durability and color developability, the polymerization initiator is an electron donor. It is preferable to include a mold polymerization initiator.

<< Electron-donating polymerization initiator >>
The electron-donating polymerization initiator is a radical by donating one electron by intermolecular electron transfer to an orbit where one electron is missing from the infrared absorber when the electrons of the infrared absorber are excited or moved intramolecularly by infrared exposure. Is a compound that generates

The image recording layer preferably contains an electron donating polymerization initiator from the viewpoint of improving printing durability in a lithographic printing plate, and examples thereof include the following five types.
(I) Alkyl or aryl art complex: It is considered that a carbon-hetero bond is oxidatively cleaved to generate an active radical. Specifically, a borate compound is preferable.
(Ii) N-arylalkylamine compound: It is considered that the C—X bond on carbon adjacent to nitrogen is cleaved by oxidation to generate an active radical. X is preferably a hydrogen atom, a carboxyl group, a trimethylsilyl group or a benzyl group. Specifically, for example, N-phenylglycine (the phenyl group may or may not have a substituent), N-phenyliminodiacetic acid (the phenyl group may or may not have a substituent). May be included).
(Iii) Sulfur-containing compounds: those in which the nitrogen atom of the above-described amines is replaced with a sulfur atom can generate active radicals by the same action. Examples thereof include phenylthioacetic acid (the phenyl group may or may not have a substituent).
(Iv) Tin-containing compound: A compound in which the nitrogen atom of the above-described amines is replaced with a tin atom can generate an active radical by the same action.
(V) Sulfinic acid salts: Active radicals can be generated by oxidation. Specific examples include arylsulfin sodium.

Among these, the image recording layer preferably contains a borate compound as an electron-donating polymerization initiator from the viewpoint of printing durability and color developability.
The borate compound is preferably a tetraaryl borate compound or a monoalkyltriaryl borate compound, more preferably a tetraaryl borate compound from the viewpoint of printing durability and color developability.
Although there is no restriction | limiting in particular as a counter cation which a borate compound has, It is preferable that they are an alkali metal ion or a tetraalkylammonium ion, and it is more preferable that they are a sodium ion, a potassium ion, or a tetrabutylammonium ion.

  Specific examples of the borate compound include sodium tetraphenylborate.

Only one kind of electron donating polymerization initiator may be added, or two or more kinds may be used in combination.
The content of the electron donating polymerization initiator is preferably 0.01% by mass to 30% by mass and more preferably 0.05% by mass to 25% by mass with respect to the total mass of the image recording layer. Preferably, it is 0.1 mass%-20 mass%.

<< Electron Accepting Polymerization Initiator >>
The polymerization initiator preferably includes an electron-accepting polymerization initiator from the viewpoint of printing durability and color development, and more preferably includes an electron-donating polymerization initiator and an electron-accepting polymerization initiator. More preferably, it comprises an electron donating polymerization initiator and an electron accepting polymerization initiator.
The electron-accepting polymerization initiator is a compound that generates a radical by accepting one electron by intermolecular electron transfer when electrons of the infrared absorber are excited by infrared exposure.

As the electron-accepting polymerization initiator, an onium salt compound is preferable.
The electron-accepting polymerization initiator may be used alone or in combination of two or more.
Examples of the electron accepting polymerization initiator include (a) organic halides, (b) carbonyl compounds, (c) azo compounds, (d) organic peroxides, (e) metallocene compounds, (f) azide compounds, (G) hexaarylbiimidazole compounds, (i) disulfone compounds, (j) oxime ester compounds, (k) onium salt compounds.

As the (a) organic halide, for example, compounds described in paragraphs 0022 to 0023 of JP-A-2008-195018 are preferable.
(B) As the carbonyl compound, for example, compounds described in paragraph 0024 of JP-A-2008-195018 are preferable.
(C) As the azo compound, for example, an azo compound described in JP-A-8-108621 can be used.
(D) As the organic peroxide, for example, compounds described in paragraph 0025 of JP-A-2008-195018 are preferable.
As the (e) metallocene compound, for example, the compound described in paragraph 0026 of JP-A-2008-195018 is preferable.
Examples of the (f) azide compound include 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
(G) As the hexaarylbiimidazole compound, for example, the compound described in paragraph 0027 of JP2008-195018A is preferable.
Examples of (i) disulfone compounds include the compounds described in JP-A Nos. 61-166544 and 2002-328465.
(J) As the oxime ester compound, for example, compounds described in paragraphs 0028 to 0030 of JP-A-2008-195018 are preferable.

Among the electron-accepting polymerization initiators, oxime ester compounds and onium salt compounds are preferable from the viewpoint of curability. Among these, from the viewpoint of printing durability, iodonium salt compounds, sulfonium salt compounds or azinium salt compounds are preferred, iodonium salt compounds or sulfonium salt compounds are more preferred, and iodonium salt compounds are particularly preferred.
Specific examples of these compounds are shown below, but the present disclosure is not limited thereto.

  As an example of the iodonium salt compound, a diaryl iodonium salt compound is preferable, and a diphenyl iodonium salt compound substituted with an electron donating group such as an alkyl group or an alkoxyl group is more preferable, and an asymmetric diphenyl iodonium salt compound is preferable. . Specific examples include diphenyliodonium = hexafluorophosphate, 4-methoxyphenyl-4- (2-methylpropyl) phenyliodonium = hexafluorophosphate, 4- (2-methylpropyl) phenyl-p-tolyliodonium = hexa. Fluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium = tetrafluoroborate, 4-octyloxy Phenyl-2,4,6-trimethoxyphenyliodonium = 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, bis ( -t- butylphenyl) iodonium hexafluorophosphate and the like.

  As an example of the sulfonium salt compound, a triarylsulfonium salt compound is preferable, and in particular, an electron-withdrawing group, for example, a triarylsulfonium salt compound in which at least a part of groups on the aromatic ring is substituted with a halogen atom is preferable. More preferred are triarylsulfonium salt compounds in which the total number of halogen atoms on the ring is 4 or more. Specific examples include triphenylsulfonium = hexafluorophosphate, triphenylsulfonium = benzoylformate, bis (4-chlorophenyl) phenylsulfonium = benzoylformate, bis (4-chlorophenyl) -4-methylphenylsulfonium = tetrafluoro. Borate, tris (4-chlorophenyl) sulfonium = 3,5-bis (methoxycarbonyl) benzenesulfonate, tris (4-chlorophenyl) sulfonium = hexafluorophosphate, tris (2,4-dichlorophenyl) sulfonium = hexafluorophos Fart.

Moreover, as a counter anion of an iodonium salt compound and a sulfonium salt compound, a sulfonamide anion or a sulfonimide anion is preferable, and a sulfonimide anion is more preferable.
Preferable examples of the sulfonamide anion or the sulfonimide anion include the sulfonamide anion or the sulfonimide anion in the compound represented by the formula 1 described above.

  The content of the electron accepting polymerization initiator is preferably 0.1% by mass to 50% by mass and more preferably 0.5% by mass to 30% by mass with respect to the total mass of the image recording layer. It is particularly preferably 0.8% by mass to 20% by mass.

  When the polymerization initiator includes an electron donating polymerization initiator and an electron accepting polymerization initiator, the electron donating polymerizable initiator and the electron accepting polymerization initiator may form a counter salt, Each of the donor-type polymerizable initiator and the electron-accepting polymerization initiator may form a salt.

-Polymerizable compound-
The image recording layer contains a polymerizable compound.
The polymerizable compound used in the present disclosure may be, for example, a radical polymerizable compound or a cationic polymerizable compound, but an addition polymerizable compound having at least one ethylenically unsaturated bond (ethylenic compound) An unsaturated compound) is preferable. The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds. The polymerizable compound has a chemical form such as a monomer, a prepolymer, i.e., a dimer, a trimer or an oligomer, or a mixture thereof.

  Examples of monomers include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), esters and amides thereof, preferably unsaturated carboxylic acids. Esters of an acid and a polyhydric alcohol compound and amides of an unsaturated carboxylic acid and a polyamine compound are used. Also, addition reaction products of unsaturated carboxylic acid esters or amides having a nucleophilic substituent such as hydroxy group, amino group, mercapto group and the like with monofunctional or polyfunctional isocyanates or epoxies, and monofunctional or polyfunctional A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. In addition, an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an isocyanate group or an epoxy group and an addition reaction product of a monofunctional or polyfunctional alcohol, amine or thiol, further a halogen atom, A substitution reaction product of an unsaturated carboxylic acid ester or amide having a leaving substituent such as a tosyloxy group and a monofunctional or polyfunctional alcohol, amine or thiol is also suitable. As another example, a compound group in which the unsaturated carboxylic acid is replaced with unsaturated phosphonic acid, styrene, vinyl ether or the like can be used. These are disclosed in JP-T-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, JP-A-9-179297. JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, It is described in Japanese Laid-Open Patent Publication No. 10-333321.

  Specific examples of the monomer of the ester of a polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, Examples include trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate, isocyanuric acid ethylene oxide (EO) -modified triacrylate, and polyester acrylate oligomer. Methacrylic acid esters include tetramethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, pentaerythritol trimethacrylate, bis [p- (3-methacryloxy-2-hydroxypropoxy) phenyl] Examples include dimethylmethane and bis [p- (methacryloxyethoxy) phenyl] dimethylmethane. Specific examples of amide monomers of polyvalent amine compounds and unsaturated carboxylic acids include methylene bisacrylamide, methylene bismethacrylamide, 1,6-hexamethylene bisacrylamide, 1,6-hexamethylene bismethacrylamide, Examples include diethylenetriamine trisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.

Also suitable are urethane-based addition polymerizable compounds produced using an addition reaction of isocyanate and hydroxy groups. Specific examples thereof include, for example, 2 molecules per molecule described in JP-B-48-41708. A vinyl urethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxy group represented by the following formula (M) to a polyisocyanate compound having one or more isocyanate groups Etc.
CH ₂ ═C (R ^M4 ) COOCH ₂ CH (R ^M5 ) OH (M)
In formula (M), R ^M4 and R ^M5 each independently represent a hydrogen atom or a methyl group.

  Further, urethane acrylates described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, JP-A-2006-65210, Ethylene described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417, JP-B-62-39418, JP-A-2000-250211, and JP-A-2007-94138 Urethane compounds having an oxide-based skeleton, urethane compounds having hydrophilic groups described in US Pat. No. 7,153,632, JP-T 8-505958, JP-A 2007-293221, and JP-A 2007-293223 Are also suitable.

Details of the method of use such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added can be arbitrarily set.
The content of the polymerizable compound is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and more preferably 15% by mass to 60% by mass with respect to the total mass of the image recording layer. It is particularly preferable that the content is% by mass.

-Acid color former-
The image recording layer contains an acid color former.
The “acid color former” used in the present disclosure means a compound having a property of developing color when heated in a state of accepting an electron accepting compound (for example, proton such as acid). As the acid color former, in particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, and the like. Compounds are preferred.

  Examples of such acid color formers include 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide (referred to as “crystal violet lactone”), 3,3-bis (4- Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1 , 2-Dimethylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-3) -Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis 9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl)- 3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide,

  3,3-bis [1,1-bis (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis ( 4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis [1- (4-dimethylaminophenyl) -1- (4-methoxyphenyl) Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-pyrrolidinophenyl) -1- (4-methoxyphenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3- [1,1-di (1-ethyl-2-methylindol-3-yl) ethylene-2-yl] -3- (4-diethylaminophenyl) ) Phthalide, 3- [1,1-di (1-ethyl-2-methyl) Indol-3-yl) ethylene-2-yl] -3- (4-N-ethyl-N-phenylaminophenyl) phthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-n- Octyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-octyl-2-methylindol-3-yl) phthalide, 3- (2-methyl-4-diethylaminophenyl) -3 Phthalides such as-(1-n-octyl-2-methylindol-3-yl) phthalide,

  4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucooramine, N-2,4,5-trichlorophenylleucooramine, rhodamine-B-anilinolactam, rhodamine- (4-nitroanilino ) Lactam, rhodamine-B- (4-chloroanilino) lactam, 3,7-bis (diethylamino) -10-benzoylphenoxazine, benzoylleucomethylene blue, 4-nitrobenzoylmethylene blue,

  3,6-dimethoxyfluorane, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3 -Diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-N-cyclohexyl-Nn-butylamino-7-methylfluorane, 3-diethylamino-7- Dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-di-n-hexylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7- ( 2'-fluorophenylamino) fluorane, 3-diethylamino- -(2'-chlorophenylamino) fluorane, 3-diethylamino-7- (3'-chlorophenylamino) fluorane, 3-diethylamino-7- (2 ', 3'-dichlorophenylamino) fluorane, 3-diethylamino-7- ( 3'-trifluoromethylphenylamino) fluorane, 3-di-n-butylamino-7- (2'-fluorophenylamino) fluorane, 3-di-n-butylamino-7- (2'-chlorophenylamino) Fluorane, 3-N-isopentyl-N-ethylamino-7- (2′-chlorophenylamino) fluorane,

  3-Nn-hexyl-N-ethylamino-7- (2'-chlorophenylamino) fluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6- Chloro-7-anilinofluorane, 3-diethylamino-6-methoxy-7-anilinofluorane, 3-di-n-butylamino-6-ethoxy-7-anilinofluorane, 3-pyrrolidino-6 Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-morpholino-6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7- Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n Pentylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-methylamino-6-methyl-7-anilinofluorane, 3-Nn-propyl-N-methylamino-6 -Methyl-7-anilinofluorane, 3-Nn-propyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-Nn-butyl-N-methylamino-6-methyl -7-anilinofluorane, 3-Nn-butyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isobutyl-N-methylamino-6-methyl-7-ani Linofluorane, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3- Nn-hexy -N-methylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-propyl Amino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-butylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-hexylamino- 6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-octylamino-6-methyl-7-anilinofluorane,

  3-N- (2′-methoxyethyl) -N-methylamino-6-methyl-7-anilinofluorane, 3-N- (2′-methoxyethyl) -N-ethylamino-6-methyl-7 -Anilinofluorane, 3-N- (2'-methoxyethyl) -N-isobutylamino-6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-methylamino -6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) ) -N-methylamino-6-methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3′-Ethoxypropyl) -N-me Ruamino-6-methyl-7-anilinofluorane, 3-N- (3′-ethoxypropyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (2′-tetrahydro Furfuryl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (4′-methylphenyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3- Diethylamino-6-ethyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3′-methylphenylamino) fluorane, 3-diethylamino-6-methyl-7- (2 ′, 6′- Dimethylphenylamino) fluorane, 3-di-n-butylamino-6-methyl-7- (2 ′, 6′-dimethylphenylamino) fluorane, 3-di-n-butylamino-7- ( ', 6'-dimethylphenylamino) fluorane, 2,2-bis [4'-(3-N-cyclohexyl-N-methylamino-6-methylfluorane) -7-ylaminophenyl] propane, 3- [ Fluoranes such as 4 ′-(4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluorane, 3- [4 ′-(dimethylaminophenyl)] amino-5,7-dimethylfluorane ,

  3- (2-Methyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-n-propoxycarbonylamino-4-di-n) -Propylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-methylamino-4-di-n-propylaminophenyl) -3- (1 -Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-methyl-4-di-n-hexylaminophenyl) -3- (1-n-octyl-2-methylindole-3- Yl) -4,7-diazaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (1-n-octyl-2-methylindole- -Yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4) -Diethylaminophenyl) -3- (1-octyl-2-methylindol-3-yl) -4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2- Methylindol-3-yl) -4 or 7-azaphthalide, 3- (2-hexyloxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4 or 7-azaphthalide 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide, 3 (2-butoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3 -Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran-3,6-bis (dimethylamino) fluorene-9 Phthalides such as -spiro-3 '-(6'-dimethylamino) phthalide, 3,6-bis (diethylamino) fluorene-9-spiro-3'-(6'-dimethylamino) phthalide,

  Others 2'-anilino-6 '-(N-ethyl-N-isopentyl) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen-3-one, 2'-anilino -6 '-(N-ethyl-N- (4-methylphenyl)) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen] -3-one, 3'-N , N-dibenzylamino-6′-N, N-diethylaminospiro [isobenzofuran-1 (3H), 9 ′-(9H) xanthen] -3-one, 2 ′-(N-methyl-N-phenyl) And amino-6 ′-(N-ethyl-N- (4-methylphenyl)) aminospiro [isobenzofuran-1 (3H), 9 ′-(9H) xanthen] -3-one.

Among these, the acid color former used in the present disclosure is at least one compound selected from the group consisting of a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound from the viewpoint of color developability. preferable.
The hue of the dye after color development is preferably green, blue or black from the viewpoint of visibility.

  It is also possible to use commercially available products as acid color formers, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H -3035, BLUE203, ATP, H-1046, H-2114 (Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF TH-107 (above, manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green -118, Red-40, Red-8 (manufactured by Yamamoto Chemicals Co., Ltd.), crystal violet lactone (manufactured by Tokyo Chemicals Industry Co., Ltd.), and the like. Among these commercial products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63 , GN-169, and crystal violet lactone are preferable because the formed film has good visible light absorption.

These acid color formers may be used alone or in combination of two or more components.
The content of the acid color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass with respect to the total mass of the image recording layer.

-Polymer particles-
The image recording layer may contain polymer particles.
The polymer particles may be selected from the group consisting of thermoplastic polymer particles, thermoreactive polymer particles, polymer particles having a polymerizable group, microcapsules containing a hydrophobic compound, and microgel (crosslinked polymer particles). preferable. Of these, polymer particles or microgels having a polymerizable group are preferred. In particularly preferred embodiments, the polymer particles comprise at least one ethylenically unsaturated polymerizable group. The presence of such polymer particles provides the effect of improving the printing durability of the exposed portion and the on-press developability of the unexposed portion.
The polymer particles are preferably thermoplastic polymer particles.

Thermoplastic polymer particles include Research Disclosure No. 1 of January 1992. 33303, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250, and European Patent No. 931647 are preferable.
Specific examples of the polymer constituting the thermoplastic polymer particles include ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, and a polyalkylene structure. Mention may be made of homopolymers or copolymers of monomers such as acrylates or methacrylates or mixtures thereof. Preferably, a copolymer containing polystyrene, styrene and acrylonitrile, or polymethyl methacrylate can be used. The average particle diameter of the thermoplastic polymer particles is preferably 0.01 μm to 3.0 μm.

  Examples of the thermally reactive polymer particles include polymer particles having a thermally reactive group. The thermoreactive polymer particles form a hydrophobized region by crosslinking due to thermal reaction and a functional group change at that time.

  The thermally reactive group in the polymer particles having a thermally reactive group may be any functional group that can perform any reaction as long as a chemical bond is formed, but is preferably a polymerizable group. Ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.), cationic polymerizable group (for example, vinyl group, vinyloxy group, epoxy group, oxetanyl group, etc.), addition reaction for radical polymerization reaction An isocyanate group or a block thereof, an epoxy group, a vinyloxy group and a functional group having an active hydrogen atom as a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxy group, etc.), a carboxy group that performs a condensation reaction, and Hydroxy group or amino group as reaction partner, acid anhydride for ring-opening addition reaction, and amino as reaction partner Or such hydroxy group are preferably exemplified.

  As the microcapsule, for example, as described in JP-A Nos. 2001-277740 and 2001-277742, at least a part of the constituent components of the image recording layer is encapsulated in the microcapsule. The constituent components of the image recording layer can also be contained outside the microcapsules. The image recording layer containing a microcapsule is preferably configured so that a hydrophobic constituent component is encapsulated in the microcapsule and a hydrophilic constituent component is contained outside the microcapsule.

  The microgel (crosslinked polymer particles) can contain a part of the constituent components of the image recording layer on at least one of the surface or the inside thereof. In particular, a reactive microgel having a radical polymerizable group on its surface is preferable from the viewpoint of image forming sensitivity and printing durability.

  A known method can be applied to microencapsulate or microgel the constituent components of the image recording layer.

In addition, as polymer particles, from the viewpoint of printing durability, stain resistance and storage stability, a polyvalent isocyanate compound which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate And what is obtained by reaction of the compound which has active hydrogen is preferable.
As the polyhydric phenol compound, a compound having a plurality of benzene rings having a phenolic hydroxy group is preferable.
The compound having a compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and at least one compound selected from the group consisting of propylene glycol, glycerin and trimethylolpropane. preferable.
As resin particles obtained by the reaction of a polyhydric isocyanate compound, which is an adduct of a polyhydric phenol compound having two or more hydroxy groups in the molecule, and isophorone diisocyanate, and a compound having active hydrogen, JP-A 2012 Preferred examples include polymer particles described in paragraphs 0032 to 0095 of JP-206495A.

Further, the polymer particles have a hydrophobic main chain from the viewpoint of printing durability and solvent resistance, and i) a structural unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) It preferably contains both constituent units with pendant groups containing hydrophilic polyalkylene oxide segments.
As the hydrophobic main chain, an acrylic resin chain is preferably exemplified.
Preferable examples of the pendant cyano group include — [CH ₂ CH (C≡N) —] or — [CH ₂ C (CH ₃ ) (C≡N) —].
The constituent unit having a pendant cyano group can be easily derived from an ethylenically unsaturated monomer such as acrylonitrile or methacrylonitrile, or a combination thereof.
The alkylene oxide in the hydrophilic polyalkylene oxide segment is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide.
The number of repeating alkylene oxide structures in the hydrophilic polyalkylene oxide segment is preferably 10 to 100, more preferably 25 to 75, and still more preferably 40 to 50.
Both a structural unit having a hydrophobic main chain, i) a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a structural unit having a pendant group including a hydrophilic polyalkylene oxide segment Preferred examples of the resin particles containing include those described in paragraphs 0039 to 0068 of JP-T-2008-503365.

The average particle size of the polymer particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and still more preferably 0.10 μm to 1.0 μm. Good resolution and stability over time can be obtained within this range.
The average primary particle size of each particle in the present disclosure is measured by a light scattering method, or an electron micrograph of the particle is taken, and the total particle size of the 5,000 particles is measured on the photograph. The value shall be calculated. For non-spherical particles, the particle size value of spherical particles having the same particle area as that on the photograph is used as the particle size.
Moreover, the average particle diameter in this indication shall be a volume average particle diameter unless there is particular notice.
The content of the polymer particles is preferably 5% by mass to 90% by mass with respect to the total mass of the image recording layer.

-Binder polymer-
The image recording layer may contain a binder polymer.
As the binder polymer, a (meth) acrylic resin, a polyvinyl acetal resin, or a polyurethane resin is preferable.

Among these, a known binder polymer used for the image recording layer of the lithographic printing plate precursor can be suitably used as the binder polymer. As an example, a binder polymer (hereinafter, also referred to as an on-press development binder polymer) used in an on-press development type lithographic printing plate precursor will be described in detail.
The binder polymer for on-press development is preferably a binder polymer having an alkylene oxide chain. The binder polymer having an alkylene oxide chain may have a poly (alkylene oxide) moiety in the main chain or in the side chain. Further, it may be a graft polymer having poly (alkylene oxide) in the side chain or a block copolymer of a block composed of a poly (alkylene oxide) -containing repeating unit and a block composed of a (alkylene oxide) -free repeating unit.
When it has a poly (alkylene oxide) moiety in the main chain, a polyurethane resin is preferred. The main chain polymer having a poly (alkylene oxide) moiety in the side chain includes (meth) acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, novolac type Examples thereof include phenol resin, polyester resin, synthetic rubber, and natural rubber, and (meth) acrylic resin is particularly preferable.

  As another preferred example of the binder polymer, a polyfunctional thiol having 6 to 10 functional groups is used as a nucleus, and a polymer chain bonded to the nucleus through a sulfide bond, and the polymer chain has a polymerizable group. Examples thereof include molecular compounds (hereinafter also referred to as star polymer compounds). As the star polymer compound, for example, compounds described in JP2012-148555A can be preferably used.

The star polymer compound has a polymerizable group such as an ethylenically unsaturated bond for improving the film strength of the image portion as described in JP-A-2008-195018, the main chain or the side chain, preferably the side chain. What has in a chain | strand is mentioned. Crosslinking is formed between the polymer molecules by the polymerizable group, and curing is accelerated.
The polymerizable group is preferably an ethylenically unsaturated group such as a (meth) acryl group, a vinyl group, an allyl group or a styryl group, or an epoxy group, and a (meth) acryl group, a vinyl group or a styryl group is polymerizable. It is more preferable from the viewpoint, and a (meth) acryl group is particularly preferable. These groups can be introduced into the polymer by polymer reaction or copolymerization. For example, a reaction between a polymer having a carboxy group in the side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be used. These groups may be used in combination.

  As for the molecular weight of the binder polymer, the weight average molecular weight (Mw) is preferably 2,000 or more, more preferably 5,000 or more, as a polystyrene conversion value by GPC method, and 10,000 to 300,000. More preferably it is.

  If necessary, hydrophilic polymers such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination. Further, a lipophilic polymer and a hydrophilic polymer can be used in combination.

In the image recording layer used in the present disclosure, the binder polymer may be used alone or in combination of two or more.
The binder polymer can be contained in an arbitrary amount in the image recording layer, but the content of the binder polymer is preferably 1% by mass to 90% by mass with respect to the total mass of the image recording layer. More preferably, it is 5 mass%-80 mass%.

-Chain transfer agent-
The image recording layer used in the present disclosure may contain a chain transfer agent. The chain transfer agent contributes to the improvement of printing durability in a lithographic printing plate.
The chain transfer agent is preferably a thiol compound, more preferably a thiol having 7 or more carbon atoms from the viewpoint of boiling point (difficult to volatilize), and still more preferably a compound having a mercapto group on the aromatic ring (aromatic thiol compound). The thiol compound is preferably a monofunctional thiol compound.

  Specific examples of the chain transfer agent include the following compounds.

A chain transfer agent may add only 1 type or may use 2 or more types together.
The content of the chain transfer agent is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass with respect to the total mass of the image recording layer, and 0.1% by mass to 30% by mass. % Is more preferable.

-Low molecular weight hydrophilic compounds-
The image recording layer may contain a low molecular weight hydrophilic compound in order to improve on-press developability while suppressing a decrease in printing durability. The low molecular weight hydrophilic compound is preferably a compound having a molecular weight of less than 1,000, more preferably a compound having a molecular weight of less than 800, and still more preferably a compound having a molecular weight of less than 500.
Examples of the low molecular weight hydrophilic compound include water-soluble organic compounds such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and the like and ether or ester derivatives thereof, glycerin, Polyols such as pentaerythritol and tris (2-hydroxyethyl) isocyanurate, organic amines such as triethanolamine, diethanolamine and monoethanolamine and salts thereof, organic sulfones such as alkylsulfonic acid, toluenesulfonic acid and benzenesulfonic acid Acids and salts thereof, organic sulfamic acids such as alkylsulfamic acid and salts thereof, organic sulfuric acids such as alkylsulfuric acid and alkylethersulfuric acid and salts thereof, phenylphosphonic acid Organic phosphonic acids and salts thereof, tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, organic carboxylic acids and salts thereof such as amino acids, betaines, and the like.

  The low molecular weight hydrophilic compound preferably contains at least one selected from polyols, organic sulfates, organic sulfonates, and betaines.

  Specific examples of organic sulfonates include alkyl sulfonates such as sodium n-butyl sulfonate, sodium n-hexyl sulfonate, sodium 2-ethylhexyl sulfonate, sodium cyclohexyl sulfonate, sodium n-octyl sulfonate; 5 , 8,11-Trioxapentadecane-1-sulfonic acid sodium salt, 5,8,11-trioxaheptadecane-1-sulfonic acid sodium salt, 13-ethyl-5,8,11-trioxaheptadecane-1-sulfone Alkyl sulfonates containing ethylene oxide chains such as sodium acid, sodium 5,8,11,14-tetraoxatetracosane-1-sulfonate; sodium benzenesulfonate, sodium p-toluenesulfonate, p-hydroxybenzenesulfonic acid Nat , Sodium p-styrenesulfonate, dimethyl-5-sulfonate sodium isophthalate, sodium 1-naphthylsulfonate, sodium 4-hydroxynaphthylsulfonate, disodium 1,5-naphthalenedisulfonate, 1,3,6- Examples thereof include aryl sulfonates such as trisodium naphthalene trisulfonate, compounds described in paragraphs 0026 to 0031 of JP-A-2007-276454 and paragraphs 0020 to 0047 of JP-A-2009-154525. The salt may be a potassium salt or a lithium salt.

  Examples of organic sulfates include sulfates of alkyl, alkenyl, alkynyl, aryl or heterocyclic monoethers of polyethylene oxide. The number of ethylene oxide units is preferably 1 to 4, and the salt is preferably a sodium salt, potassium salt or lithium salt. Specific examples include the compounds described in paragraphs 0034 to 0038 of JP-A-2007-276454.

  As the betaines, compounds having 1 to 5 carbon atoms of the hydrocarbon substituent on the nitrogen atom are preferable, and specific examples thereof include trimethylammonium acetate, dimethylpropylammonium acetate, 3-hydroxy-4-trimethylammonium. Obtylate, 4- (1-pyridinio) butyrate, 1-hydroxyethyl-1-imidazolioacetate, trimethylammonium methanesulfonate, dimethylpropylammonium methanesulfonate, 3-trimethylammonio-1-propanesulfonate, 3 -(1-pyridinio) -1-propanesulfonate and the like.

  Since low molecular weight hydrophilic compounds have a small hydrophobic part structure and almost no surface activity, dampening water penetrates into the exposed part of the image recording layer (image part) and decreases the hydrophobicity and film strength of the image part. The ink receptivity and printing durability of the image recording layer can be maintained satisfactorily.

The content of the low molecular weight hydrophilic compound is preferably 0.5% by mass to 20% by mass, more preferably 1% by mass to 15% by mass with respect to the total mass of the image recording layer, and 2% by mass to 10% by mass. Is more preferable. In this range, good on-press developability and printing durability can be obtained.
A low molecular weight hydrophilic compound may be used individually by 1 type, and 2 or more types may be mixed and used for it.

-Grease-sensitizing agent-
The image recording layer may contain a sensitizing agent such as a phosphonium compound, a nitrogen-containing low molecular weight compound, or an ammonium group-containing polymer in order to improve the inking property. In particular, when an inorganic layered compound is contained in the protective layer, these compounds function as a surface coating agent for the inorganic layered compound, and can suppress a decrease in the inking property during printing by the inorganic layered compound.
As the sensitizer, it is preferable to use a phosphonium compound, a nitrogen-containing low molecular weight compound, and an ammonium group-containing polymer in combination, and use a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer in combination. Is more preferable.

  Examples of the phosphonium compound include phosphonium compounds described in JP-A-2006-297907 and JP-A-2007-50660. Specific examples include tetrabutylphosphonium iodide, butyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, 1,4-bis (triphenylphosphonio) butanedi (hexafluorophosphate), 1,7-bis (tri Phenylphosphonio) heptane = sulfate, 1,9-bis (triphenylphosphonio) nonane = naphthalene-2,7-disulfonate, and the like.

  Examples of nitrogen-containing low molecular weight compounds include amine salts and quaternary ammonium salts. Also included are imidazolinium salts, benzimidazolinium salts, pyridinium salts, and quinolinium salts. Of these, quaternary ammonium salts and pyridinium salts are preferred. Specific examples include tetramethylammonium = hexafluorophosphate, tetrabutylammonium = hexafluorophosphate, dodecyltrimethylammonium = p-toluenesulfonate, benzyltriethylammonium = hexafluorophosphate, benzyldimethyloctylammonium = hexafluorophosphate. And the compounds described in paragraphs 0021 to 0037 of JP2008-284858A, paragraphs 0030 to 0057 of JP2009-90645A, and the like.

  As an ammonium group containing polymer, what is necessary is just to have an ammonium group in the structure, and the polymer which contains 5 mol%-80 mol% of (meth) acrylate which has an ammonium group in a side chain as a copolymerization component is preferable. Specific examples include the polymers described in paragraphs 0089 to 0105 of JP2009-208458A.

  The ammonium salt-containing polymer preferably has a reduced specific viscosity (unit: ml / g) determined in accordance with the measuring method described in JP-A-2009-208458, in the range of 5 to 120, and in the range of 10 to 110. Are more preferable, and those in the range of 15 to 100 are particularly preferable. When the said reduced specific viscosity is converted into a weight average molecular weight (Mw), 10,000-150,000 are preferable, 17,000-140,000 are more preferable, 20,000-130,000 are especially preferable.

Specific examples of the ammonium group-containing polymer are shown below.
(1) 2- (Trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90, Mw 45,000)
(2) 2- (Trimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(3) 2- (Ethyldimethylammonio) ethyl methacrylate = p-toluenesulfonate / hexyl methacrylate copolymer (molar ratio 30/70, Mw 45,000)
(4) 2- (Trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(5) 2- (Trimethylammonio) ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40/60, Mw 7 million)
(6) 2- (Butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25/75, Mw 650,000)
(7) 2- (Butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 650,000)
(8) 2- (Butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 , Mw75,000)
(9) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate / 2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar ratio 15/80/5 , Mw 650,000)

  The content of the sensitizing agent is preferably 0.01% by mass to 30.0% by mass, more preferably 0.1% by mass to 15.0% by mass with respect to the total mass of the image recording layer, and 1% by mass. % To 10% by mass is more preferable.

-Other ingredients-
The image recording layer can contain, as other components, a surfactant, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic particles, an inorganic layered compound, and the like. Specifically, reference can be made to the descriptions in paragraphs 0114 to 0159 of JP-A-2008-284817.

-Formation of image recording layer-
The image recording layer in the lithographic printing plate precursor according to the present disclosure is applied by dispersing or dissolving the necessary components in a known solvent as described in paragraphs 0142 to 0143 of JP-A-2008-195018, for example. It can be formed by preparing a liquid, applying the coating liquid onto a support by a known method such as bar coater coating, and drying. Coating, the coating amount of the image recording layer after drying (solid content) may be varied according to the intended ^{purpose, 0.3g / m 2 ~3.0g / m} 2 is preferred. Within this range, good sensitivity and good film characteristics of the image recording layer can be obtained.
A known solvent can be used as the solvent. Specifically, for example, water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3- Methoxy-1-propanol, methoxymethoxy Tanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone , Methyl lactate, ethyl lactate and the like. A solvent may be used individually by 1 type and may use 2 or more types together. The solid content concentration in the coating solution is preferably about 1 to 50% by mass.
The coating amount (solid content) of the image recording layer after coating and drying varies depending on the use, but from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer, about 0.3 to 3.0 g / m ^2. Is preferred.

<Hydrophilic support>
The hydrophilic support (hereinafter also simply referred to as “support”) in the lithographic printing plate precursor according to the present disclosure can be appropriately selected from known hydrophilic supports for lithographic printing plate precursors. As the hydrophilic support, an aluminum plate which has been roughened and anodized by a known method is preferable.
If necessary, the aluminum plate is further subjected to micropore enlargement treatment or sealing treatment of an anodized film described in JP-A Nos. 2001-253181 and 2001-322365, U.S. Pat. No. 2,714, Surface hydrophilization treatment with alkali metal silicate as described in US Pat. Nos. 066, 3,181,461, 3,280,734 and 3,902,734, US The surface hydrophilization treatment with polyvinyl phosphonic acid as described in the specifications of Patent Nos. 3,276,868, 4,153,461 and 4,689,272 is appropriately selected. You may go.
The support preferably has a center line average roughness of 0.10 μm to 1.2 μm.

  If necessary, the support is provided on the surface opposite to the image recording layer, such as an organic polymer compound described in JP-A-5-45885, or an alkoxy compound of silicon described in JP-A-6-35174. You may have the backcoat layer containing.

<Undercoat layer>
The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes referred to as an intermediate layer) between the image recording layer and the support. The undercoat layer enhances the adhesion between the support and the image recording layer in the exposed area, and easily peels off the image recording layer from the support in the unexposed area. It contributes to improving. In addition, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, and thus has an effect of preventing the heat generated by the exposure from diffusing to the support and lowering the sensitivity.

  Examples of the compound used for the undercoat layer include polymers having an adsorptive group and a hydrophilic group that can be adsorbed on the support surface. In order to improve the adhesion to the image recording layer, a polymer having an adsorptive group and a hydrophilic group and further having a crosslinkable group is preferable. The compound used for the undercoat layer may be a low molecular compound or a polymer. The compounds used for the undercoat layer may be used as a mixture of two or more if necessary.

When the compound used for the undercoat layer is a polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferable.
Examples of the adsorptive group that can be adsorbed on the support surface include a phenolic hydroxy group, a carboxy group, —PO ₃ H ₂ , —OPO ₃ H ₂ , —CONHSO ₂ —, —SO ₂ NHSO ₂ —, —COCH ₂ COCH _3. Is preferred. As the hydrophilic group, a sulfo group or a salt thereof, or a salt of a carboxy group is preferable. As the crosslinkable group, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, and the like are preferable.
The polymer may have a crosslinkable group introduced by salt formation between a polar substituent of the polymer, a substituent having a counter charge with the polar substituent and a compound having an ethylenically unsaturated bond, Other monomers, preferably hydrophilic monomers may be further copolymerized.

Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679 and an ethylenic compound described in JP-A-2-304441. The phosphorus compound which has a heavy bond reactive group is mentioned suitably. Crosslinkable groups (preferably ethylenically unsaturated bond groups) described in JP 2005-238816 A, JP 2005-12549 A, JP 2006-239867 A, JP 2006-215263 A, and Supports A low molecular or high molecular compound having a functional group interacting with the surface and a hydrophilic group is also preferably used.
More preferable are polymer polymers having an adsorbing group, a hydrophilic group and a crosslinkable group which can be adsorbed on the surface of the support described in JP-A Nos. 2005-125749 and 2006-188038.

The content of the ethylenically unsaturated bond group in the polymer used for the undercoat layer is preferably 0.1 mmol to 10.0 mmol, more preferably 0.2 mmol to 5.5 mmol per 1 g of the polymer.
The weight average molecular weight (Mw) of the polymer used for the undercoat layer is preferably 5,000 or more, and more preferably 10,000 to 300,000.

  In addition to the above compound for the undercoat layer, the undercoat layer is a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group, or a functional group having a polymerization inhibitory ability and a support surface in order to prevent contamination with time. And a compound having a group that interacts with (for example, 1,4-diazabicyclo [2.2.2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, hydroxy Ethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, and the like).

The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is ^preferably from ^{0.1mg / m 2 ~100mg / m 2} , 1mg / m 2 ~30mg / m 2 is more preferable.

<Protective layer>
The lithographic printing plate precursor according to the present disclosure preferably has a protective layer (sometimes referred to as an overcoat layer) on the image recording layer. In addition to the function of suppressing the image formation inhibition reaction by blocking oxygen, the protective layer has a function of preventing scratches in the image recording layer and preventing ablation during high-illuminance laser exposure.

The protective layer having such characteristics is described in, for example, US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low oxygen permeability polymer used for the protective layer, either a water-soluble polymer or a water-insoluble polymer can be appropriately selected and used, and two or more types can be mixed and used as necessary. it can. Specific examples include polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble cellulose derivatives, poly (meth) acrylonitrile, and the like.
As the modified polyvinyl alcohol, acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used. Specific examples include modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

The protective layer preferably contains an inorganic layered compound in order to enhance oxygen barrier properties. The inorganic layered compound is a particle having a thin flat plate shape, for example, mica group such as natural mica, synthetic mica, talc, teniolite, montmorillonite, saponite, hector represented by the formula: 3MgO · 4SiO · H ₂ O Light, zirconium phosphate, etc. are mentioned.
The inorganic layered compound preferably used is a mica compound. As the mica compound, for example, the formula: A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [where A is one of K, Na, Ca, B and C are One of Fe (II), Fe (III), Mn, Al, Mg, and V, and D is Si or Al. ] Mica groups such as natural mica and synthetic mica represented by

In the mica group, natural mica includes muscovite, soda mica, phlogopite, biotite, and sericite. As the synthetic mica, non-swelling mica such as fluor-phlogopite mica KMg ₃ (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicon mica KMg _2.5 Si ₄ O ₁₀ ) F ₂ , and Na tetrasilicic mica NaMg2 _{. 5} (Si ₄ O ₁₀ ) F ₂ , Na or Li teniolite (Na, Li) Mg ₂ Li (Si ₄ O ₁₀ ) F ₂ , montmorillonite-based Na or Li hectorite (Na, Li) _1/8 Mg _{2 /} Examples include swellable mica, such as ₅ Li _1/8 (Si ₄ O ₁₀ ) F ₂ . Synthetic smectite is also useful.

Of the mica compounds, fluorine-based swellable mica is particularly useful. That is, the swellable synthetic mica has a laminated structure composed of unit crystal lattice layers with a thickness of about 10 to 15 (1Å = 0.1 nm), and the substitution of metal atoms in the lattice is significantly larger than other clay minerals. As a result, the lattice layer is deficient in positive charge, and in order to compensate for this, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , and Mg ²⁺ are adsorbed between the layers. The cations present between these layers are called exchangeable cations and can be exchanged with various cations. In particular, when the cation between the layers is Li ⁺ or Na ⁺ , the bond between the layered crystal lattices is weak because the ionic radius is small, and the layer swells greatly with water. If shear is applied in this state, it will be easily cleaved to form a stable sol in water. Swelling synthetic mica has a strong tendency and is particularly preferably used.

  As the shape of the mica compound, from the viewpoint of diffusion control, the thinner the better, the better the plane size as long as the smoothness of the coated surface and the transmittance of actinic rays are not impaired. Accordingly, the aspect ratio is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, and can be measured, for example, from a projection drawing of a particle by a micrograph. The larger the aspect ratio, the greater the effect that can be obtained.

  The average major axis of the mica compound has a mean major axis of preferably 0.3 μm to 20 μm, more preferably 0.5 μm to 10 μm, and particularly preferably 1 μm to 5 μm. The average thickness of the particles is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. Specifically, for example, in the case of swellable synthetic mica, which is a representative compound, preferred embodiments have a thickness of about 1 nm to 50 nm and a surface size (major axis) of about 1 μm to 20 μm.

  1 mass%-60 mass% are preferable with respect to the total solid of a protective layer, and, as for content of an inorganic layered compound, 3 mass%-50 mass% are more preferable. Even when a plurality of types of inorganic layered compounds are used in combination, the total amount of the inorganic layered compounds is preferably the above content. Within the above range, the oxygen barrier property is improved and good sensitivity is obtained. Further, it is possible to prevent a decrease in inking property.

  The protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, and inorganic particles for controlling the slipperiness of the surface. Further, the protective layer may contain the sensitizer described in the image recording layer.

The protective layer is applied by a known method. The coating amount of the protective layer (solid content) is ^preferably from ^{0.01g / m 2 ~10g / m 2} , more preferably ^{0.02g / m 2 ~3g / m 2} , 0.02g / m 2 ~1g / m ² is particularly preferred.

(Preparation method of lithographic printing plate)
A lithographic printing plate can be produced by subjecting the lithographic printing plate precursor according to the present disclosure to image exposure and development.
The method for producing a lithographic printing plate according to the present disclosure includes a step of exposing the lithographic printing plate precursor according to the present disclosure imagewise to form an exposed portion and an unexposed portion (hereinafter also referred to as “exposure step”), And it is preferable to include the process (henceforth an "on-press development process") which removes the said unexposed part by supplying at least one of printing ink and dampening water in this order.
The lithographic printing plate production method according to the present disclosure includes a step of image-exposing a lithographic printing plate precursor according to the present disclosure containing a polymerization initiator and a polymerizable compound with a laser, and a one-bath developer having a pH of 2 to 11. It is preferable to include a step of removing an unexposed portion of the image recording layer.
Hereinafter, the preferable aspect of each process is demonstrated in order about the preparation method of the lithographic printing plate which concerns on this indication, and the lithographic printing method which concerns on this indication. Note that the lithographic printing plate precursor according to the present disclosure can also be developed with a developer.

<Exposure process>
The method for producing a lithographic printing plate according to the present disclosure preferably includes an exposure step of exposing the lithographic printing plate precursor according to the present disclosure imagewise to form an exposed portion and an unexposed portion. The lithographic printing plate precursor according to the present disclosure is preferably imagewise exposed by laser exposure through a transparent original having a line image, a halftone dot image or the like, or by laser beam scanning by digital data.
The wavelength of the light source is preferably 750 nm to 1,400 nm. As a light source of 750 nm to 1,400 nm, a solid laser and a semiconductor laser emitting infrared rays are suitable. For the infrared laser, the output is preferably more than 100 mW, preferably, the exposure time per pixel is preferably within 20 microseconds, also that the amount of irradiation energy is 10mJ ^/ cm ² ~300mJ ^/ cm 2 preferable. In order to shorten the exposure time, it is preferable to use a multi-beam laser device. The exposure mechanism may be any of an internal drum system, an external drum system, a flat bed system, and the like.
Image exposure can be performed by a conventional method using a plate setter or the like. In the case of on-press development, the lithographic printing plate precursor may be mounted on a printing press and then image exposure may be performed on the printing press.

<On-machine development process>
The method for producing a lithographic printing plate according to the present disclosure preferably includes an on-machine development process in which at least one of printing ink and fountain solution is supplied to remove the unexposed portions.
Further, the lithographic printing plate preparation method according to the present disclosure may be performed by a method of developing with a developer (developer processing method).
The on-machine development method will be described below.

-On-press development system-
In the on-press development method, an image-exposed lithographic printing plate precursor is supplied with oil-based ink and an aqueous component on the printing machine, and the lithographic printing plate is prepared by removing the image forming layer in the non-image area. Is preferred.
That is, after image exposure of the lithographic printing plate precursor, it is mounted on the printing machine as it is without any development processing, or the lithographic printing plate precursor is mounted on the printing machine and then image-exposed on the printing machine. When an oil-based ink and a water-based component are supplied for printing, an uncured image forming layer is formed in the non-image area at an early stage of printing by either or both of the supplied oil-based ink and water-based component. It is removed by dissolution or dispersion, and a hydrophilic surface is exposed at that portion. On the other hand, in the exposed portion, the image forming layer cured by exposure forms an oil-based ink receiving portion having a lipophilic surface. Oil-based ink or water-based component may be supplied first to the plate surface, but oil-based ink is first supplied in order to prevent the water-based component from being contaminated by components of the image forming layer from which the water-based component has been removed. It is preferable. In this way, the lithographic printing plate precursor is subjected to on-press development on a printing machine and used as it is for printing a large number of sheets. As the oil-based ink and the aqueous component, ordinary lithographic printing ink and fountain solution are preferably used.

  As the laser for image exposure of the lithographic printing plate precursor according to the present disclosure containing the polymerization initiator and the polymerizable compound, the wavelength of the light source is preferably 300 nm to 450 nm or 750 nm to 1,400 nm. In the case of a light source of 300 nm to 450 nm, a lithographic printing plate precursor containing a sensitizing dye having an absorption maximum in this wavelength region in the image recording layer is preferably used, and the above-described light source of 750 to 1,400 nm is preferably used. It is done. As the light source of 300 nm to 450 nm, a semiconductor laser is suitable.

  As the one-bath developer having a pH of 2 to 11, a known developer can be used. Examples thereof include a developer having a pH of 2 to 11 containing at least one of a surfactant and a water-soluble polymer compound. In the development processing using a conventional strong alkali developer, the protective layer is removed by a pre-water washing step, then alkali development is performed, the alkali is washed and removed by a post-water washing step, the gum solution treatment is performed, and the drying step is performed. It was necessary to do. By using the above-mentioned developer containing a surfactant or a water-soluble polymer compound, development-gum solution treatment can be performed simultaneously. Therefore, the post-water washing step is not particularly required, and the drying step can be performed after the development and gum solution treatment with one solution. Further, since the protective layer can be removed simultaneously with development and gum solution treatment, a pre-water washing step is not particularly required. After the development treatment, it is preferable to dry after removing the excess developer using a squeeze roller or the like.

<Printing process>
The lithographic printing method according to the present disclosure includes a printing step of printing a recording medium by supplying printing ink to the lithographic printing plate developed on-press in the on-press development step.
The printing ink is not particularly limited, and various known inks can be used as desired. Moreover, as printing ink, oil-based ink or ultraviolet curable ink (UV ink) is mentioned preferably, UV ink is mentioned more preferably.
Moreover, in the said printing process, you may supply dampening water as needed.
The printing process may be performed continuously with the on-press development process without stopping the printing press.
The recording medium is not particularly limited, and a known recording medium can be used as desired.

  In the lithographic printing plate preparation method from the lithographic printing plate precursor according to the present disclosure and the lithographic printing method according to the present disclosure, the lithographic printing is performed before exposure, during exposure, and between exposure and development, as necessary. The entire surface of the plate precursor may be heated. By such heating, an image forming reaction in the image forming layer is promoted, and advantages such as an improvement in sensitivity and printing durability and a stabilization of sensitivity may occur. Heating before development is preferably performed under mild conditions of 150 ° C. or lower. With the above aspect, problems such as curing of the non-image area can be prevented. It is preferable to use very strong conditions for heating after development, and it is preferable that the temperature is in the range of 100 ° C to 500 ° C. Within the above range, a sufficient image reinforcing action can be obtained, and problems such as deterioration of the support and thermal decomposition of the image area can be suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this embodiment in detail, this embodiment is not limited to these. In the polymer compound, unless otherwise specified, the molecular weight is a weight average molecular weight (Mw) in terms of polystyrene converted by a gel permeation chromatography (GPC) method, and the ratio of repeating units is a mole percentage. Further, “part” and “%” mean “part by mass” and “% by mass” unless otherwise specified.

Synthesis examples of the compound represented by the above formula 1 are described below. Other compounds represented by Formula 1 can also be synthesized in the same manner by appropriately changing raw materials and reaction intermediates.
Moreover, the mother nucleus structure A-1 and the like and the counter anion B-1 and the like in the compound represented by Formula 1 used in the examples have the same structure as described above.

(Examples 1-33 and Comparative Examples 1-13)
1. Preparation of lithographic printing plate precursor A

<Production of support>
In order to remove the rolling oil on the surface of an aluminum plate (material JIS A 1050) having a thickness of 0.3 mm, a degreasing treatment was performed at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution, and then the hair diameter was adjusted to 0. The surface of the aluminum plate was grained using ^three 3 mm bundled nylon brushes and a pumice-water suspension (specific gravity 1.1 g / cm ³ ) having a median diameter of 25 μm and washed well with water. Etching was performed by immersing the aluminum plate in a 25 mass% sodium hydroxide aqueous solution at 45 ° C for 9 seconds, washing with water, and further immersed in a 20 mass% nitric acid aqueous solution at 60 ° C for 20 seconds, followed by washing with water. The etching amount of the grained surface was about 3 g / m ² .

Next, an electrochemical roughening treatment was performed continuously using an alternating voltage of 60 Hz. The electrolyte was a 1% by mass aqueous nitric acid solution (containing 0.5% by mass of aluminum ions), and the liquid temperature was 50 ° C. The AC power supply waveform is electrochemical roughening treatment using a trapezoidal rectangular wave AC with a time TP of 0.8 msec until the current value reaches a peak from zero, a duty ratio of 1: 1, and a trapezoidal rectangular wave AC. Went. Ferrite was used for the auxiliary anode. The current density was 30 A / dm ² at the peak current value, and 5% of the current flowing from the power source was shunted to the auxiliary anode. The amount of electricity in nitric acid electrolysis was 175 C / dm ² when the aluminum plate was the anode. Then, water washing by spraying was performed.

Subsequently, nitric acid electrolysis was performed with an aqueous solution of 0.5% by mass of hydrochloric acid (containing 0.5% by mass of aluminum ions) and an electrolytic solution having a liquid temperature of 50 ° C. under the condition of an electric quantity of 50 C / dm ² when the aluminum plate was the anode Electrochemical roughening treatment was carried out in the same manner as above, and then water washing by spraying was performed.
Next, a 2.5 g / m ² direct current anodic oxide film having a current density of 15 A / dm ² is formed on an aluminum plate as an electrolyte using a 15 mass% aqueous sulfuric acid solution (containing 0.5 mass% of aluminum ions), and then washed with water. The support A was prepared by drying. The average pore diameter (surface average pore diameter) in the surface layer of the anodized film was 10 nm.
The measurement of the pore diameter in the surface layer of the anodized film uses an ultra-high resolution SEM (Hitachi S-900), and without performing a deposition process or the like that imparts conductivity at a relatively low acceleration voltage of 12 V. The surface was observed at a magnification of 150,000 times, and 50 pores were randomly extracted to obtain an average value. The standard deviation error was ± 10% or less.

Thereafter, in order to ensure the hydrophilicity of the non-image area, the support A was subjected to silicate treatment at 60 ° C. for 10 seconds using a 2.5 mass% No. 3 sodium silicate aqueous solution, and then washed with water to obtain the support B. Produced. The adhesion amount of Si was 10 mg / m ² . When the center line average roughness (Ra) of the support B was measured using a needle having a diameter of 2 μm, it was 0.51 μm.

  In the production of the support A, a support C was produced in the same manner as the production of the support A, except that the electrolytic solution for forming the DC anodized film was changed to a 22 mass% phosphoric acid aqueous solution. The average pore diameter (surface average pore diameter) in the surface layer of the anodized film was 25 nm as measured by the same method as described above.

Thereafter, in order to ensure the hydrophilicity of the non-image area, the support C was subjected to a silicate treatment at 60 ° C. for 10 seconds using a 2.5 mass% No. 3 sodium silicate aqueous solution, and then washed with water to obtain the support D. Produced. The adhesion amount of Si was 10 mg / m ² . When the center line average roughness (Ra) of the support D was measured using a needle having a diameter of 2 μm, it was 0.52 μm.

<Formation of undercoat layer>
An undercoat layer coating solution (1) having the following composition was applied on a support shown in Tables 1 to 3 to be described later so that the dry coating amount was 23 mg / m ² to form an undercoat layer.

<Undercoat layer coating solution (1)>
Polymer (P-1) [Structure below]: 0.18 parts Hydroxyethyliminodiacetic acid: 0.10 parts Water: 61.4 parts

  The synthesis method of polymer P-1 is described below.

(Synthesis of Monomer M-1)
200 g (0.91 mol) of Ancamine 1922A (diethylene glycol di (aminopropyl) ether, manufactured by Air Products), 435 g of distilled water and 410 g of methanol were added to a 3 L three-necked flask and cooled to 5 ° C. Next, 222.5 g (1.82 mol) of benzoic acid and 25 mg (0.15 mmol) of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO) were added, and methacrylic acid was added. 280 g (1.82 mmol) of anhydride was added dropwise so that the internal temperature of the reaction solution was 10 ° C. or lower. The reaction solution was stirred at 5 ° C. for 6 hours and then stirred at 25 ° C. for 12 hours, and then 70 g of phosphoric acid was added to adjust the pH to 3.3. The reaction solution was transferred to a 10 L stainless beaker, 3.7 L of ethyl acetate, 1.5 L of methyl-tertbutyl ether (MTBE) and 0.65 L of distilled water were added, and the mixture was vigorously stirred and allowed to stand. After discarding the upper layer (organic layer), 1.8 L of ethyl acetate was added, stirred vigorously and allowed to stand, and the upper layer was discarded. Further, 1.5 L of ethyl acetate was added, stirred vigorously and allowed to stand, and the upper layer was discarded. Next, 1.6 L of MTBE was added, and after vigorous stirring, the mixture was allowed to stand and the upper layer was discarded. 4-OH-TEMPO62.5mg (0.36mmol) was added to the obtained aqueous solution, and 1.2kg of monomer M-1 aqueous solution (20.1 mass% of solid content conversion) was obtained.

(Purification of monomer M-2)
420 g of light ester P-1M (2-methacryloylethyl acid phosphate, manufactured by Kyoeisha Chemical Co., Ltd.), 1,050 g of diethylene glycol dibutyl ether and 1,050 g of distilled water were added to a separatory funnel, and the mixture was allowed to stand after vigorous stirring. . After discarding the upper layer, 1050 g of diethylene glycol dibutyl ether was added, and the mixture was vigorously stirred and allowed to stand. The upper layer was discarded, and 1.3 kg of an aqueous solution of monomer M-2 (solid content 10.5% by mass) was obtained.

(Synthesis of polymer P-1)
To a 3 L three-necked flask, 600.6 g of distilled water, 33.1 g of an aqueous monomer M-1 solution and 46.1 g of the following monomer M-3 were added, and the temperature was raised to 55 ° C. in a nitrogen atmosphere. Next, after dropping the dropping liquid A shown below over 2 hours and stirring for 30 minutes, 3.9 g of VA-046B (manufactured by Wako Pure Chemical Industries, Ltd.) was added, the temperature was raised to 80 ° C., 1 Stir for 5 hours. After returning the reaction solution to room temperature (25 ° C., the same applies hereinafter), 175 g of a 30% by mass aqueous sodium hydroxide solution was added to adjust the pH to 8.3. Next, 152.2 mg of 4-OH-TEMPO was added and the temperature was raised to 53 ° C. 66.0 g of methacrylic anhydride was added and stirred at 53 ° C. for 3 hours. After returning to room temperature, the reaction solution was transferred to a 10 L stainless beaker, MTBE 1,800 g was added, vigorously stirred and allowed to stand, and the upper layer was discarded. Similarly, the washing operation with 1,800 g of MTBE was further repeated twice, and then 1,700 g of distilled water and 212 mg of 4-OH-TEMPO were added to the obtained aqueous layer, and polymer P-1 (solid content conversion 11) was obtained as a uniform solution. 4.0%) was obtained. The weight average molecular weight (Mw) in terms of polyethylene glycol by a gel permeation chromatography (GPC) method was 200,000.

-Drip liquid A-
-Monomer M-1 aqueous solution: 132.4 g
-Monomer M-2 aqueous solution: 376.9 g
Monomer M-3 [following structure]: 184.3 g
・ Blemmer PME4000 (manufactured by NOF Corporation): 15.3 g
・ VA-046B (manufactured by Wako Pure Chemical Industries, Ltd.): 3.9 g
・ Distilled water: 717.4g

BLEMMER PME4000: Methoxypolyethyleneglycol methacrylate (Repeating number of oxyethylene units: 90)
VA-046B: 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate

<Formation of image recording layer>
On the undercoat layer, an image recording layer coating solution (1) having the following composition was coated with a bar and oven dried at 120 ° C. for 40 seconds to form an image recording layer having a dry coating amount of 1.0 g / m ² .
The image recording layer coating solution (1) was prepared by mixing and stirring the following photosensitive solution (1) and microgel solution immediately before coating.

-Photosensitive solution (1)-
-Binder polymer (1) [following structure]: 0.125 parts-Electron-accepting polymerization initiator [following structure]: 0.132 parts-Compound represented by formula 1 described in Tables 1 to 3 or for comparison Compound (infrared absorber): 0.033 parts, electron donating polymerization initiator [following structure]: 0.057 parts, acid color former [following structure]: 0.058 parts, polymerizable compound U-15HA (urethane acrylate) Shin-Nakamura Chemical Co., Ltd.): 0.146 parts ATM-4E (ethoxylated pentaerythritol tetraacrylate, Shin-Nakamura Chemical Co., Ltd.): 0.078 parts Hydrophilic polymer hydroxypropyl cellulose ( HPC-SSL, manufactured by Nippon Soda Co., Ltd.): 0.030 part. Low molecular weight hydrophilic compound (tris (2-hydroxyethyl) isocyanurate): 0.020 part. Fluorosurfactant ( ) Having structure shown below 0.008 parts 2-Butanone 1.091 parts 1-Methoxy-2-propanol: 8.609 parts

-Microgel solution-
Microgel (1): 1.64 parts Distilled water: 2.425 parts

  The structures of the binder polymer (1), electron-accepting polymerization initiator, electron-donating polymerization initiator, and fluorine-based surfactant (1) used in the photosensitive solution (1) are shown below.

  Electron-donating polymerization initiators I-1 to I-4 (the following compounds)

  Electron-donating polymerization initiators D-1 to D-4 (the following compounds)

  Acid generators CL-1 to CL-4 (the following compounds)

  Comparative dye compounds A'-1 to A'-7 (the following compounds)

The adjustment method of the said binder polymer (1) is shown below.
To a 1 L three-necked flask, 78 g of 1-methoxy-2-propanol was added, and the temperature was adjusted to 70 ° C. under a nitrogen stream. The dropping liquid 1 shown below was dripped there over 2.5 hours, and it heated up at 80 degreeC after completion | finish of dripping, and stirred for 2 hours. Furthermore, the additive liquid 1 shown below was added, and it heated up at 90 degreeC, and stirred for 2.5 hours.

-Drip solution 1-
・ Methyl methacrylate: 21.8g
・ Blemmer PME100: 52.1g
・ Methacrylic acid: 14.2 g
Dipentaerythritol hexakis (3-mercaptopropionic acid): 2.15 g
・ V-601 (Wako Pure Chemical Industries, Ltd.): 0.38g
1-methoxy-2-propanol: 50.2 g

-Additive solution 1-
V-601 (dimethyl 2,2′-azobis (2-methylpropionate), manufactured by Wako Pure Chemical Industries, Ltd.): 0.038 g
1-methoxy-2-propanol: 4.0 g

  The reaction solution was cooled to 25 ° C., 136.6 g of 1-methoxy-2-propanol, 0.238 g of 4-OH-TEMPO, 25.88 g of glycidyl methacrylate, and 2.957 g of trimethylbenzylammonium bromide were added, and the mixture was stirred at 90 ° C. Stir for 18 hours. The resulting solution was cooled to room temperature, and diluted with 1-methoxy-2-propanol to a solid content concentration of 23% to obtain a binder polymer (1). The weight average molecular weight (Mw) in terms of polystyrene converted by gel permeation chromatography (GPC) was 40,000.

  A method for preparing the microgel (1) used in the microgel solution is shown below.

<Preparation of polyvalent isocyanate compound (1)>
In a suspension of 17.78 g (80 mmol) of isophorone diisocyanate and 7.35 g (20 mmol) of the following polyphenol compound (1) in ethyl acetate (25.31 g), bismuth tris (2-ethylhexanoate) (Neostan U -600, Nitto Kasei Co., Ltd.) 43 mg was added and stirred. When the exotherm had subsided, the reaction temperature was set to 50 ° C., and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50 mass%) of the polyvalent isocyanate compound (1).

<Preparation of microgel (1)>
The following oil phase component and aqueous phase component were mixed and emulsified for 10 minutes at 12,000 rpm using a homogenizer. After stirring the obtained emulsion at 45 ° C. for 4 hours, 10 mass of 1,8-diazabicyclo [5.4.0] undec-7-ene-octylate (U-CAT SA102, manufactured by San Apro Co., Ltd.) % Aqueous solution (5.20 g) was added, and the mixture was stirred at room temperature for 30 minutes and allowed to stand at 45 ° C. for 24 hours. Distilled water was used to adjust the solid content concentration to 20% by mass, and an aqueous dispersion of microgel (1) was obtained. When an average particle diameter was measured by a light scattering method, it was 0.28 μm.

-Oil phase component-
(Component 1) Ethyl acetate: 12.0 g
(Component 2) An adduct obtained by adding trimethylolpropane (6 mol) and xylene diisocyanate (18 mol) and adding a methyl side terminal polyoxyethylene (1 mol, repeating number of oxyethylene units: 90) to this ( 50 mass% ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.): 3.76 g
(Component 3) Polyvalent isocyanate compound (1) (as 50% by mass ethyl acetate solution): 15.0 g
(Component 4) 65 mass% ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer): 11.54 g
(Component 5) 10% ethyl acetate solution of sulfonate type surfactant (Pionin A-41-C, Takemoto Yushi Co., Ltd.): 4.42 g

-Aqueous phase component-
Distilled water: 46.87g

<Formation of protective layer>
On the image recording layer, a protective layer coating solution having the following composition was bar coated and oven dried at 120 ° C. for 60 seconds to form a protective layer having a dry coating amount of 0.15 g / m ^2. And each lithographic printing plate precursor for Comparative Examples 1 to 4 was prepared. Table 1 summarizes the support used in the preparation of each lithographic printing plate precursor, the compound represented by Formula 1 in the image recording layer coating solution (1), or the comparative compound.

-Protective layer coating solution-
-Inorganic layered compound dispersion (1) [below]: 1.5 parts-Polyvinyl alcohol (CKS50, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., sulfonic acid modification, saponification degree 99 mol% or more, polymerization degree 300) 6% by mass Aqueous solution: 0.55 parts, polyvinyl alcohol (PVA-405, manufactured by Kuraray Co., Ltd., saponification degree: 81.5 mol%, polymerization degree: 500) 6% by weight Aqueous solution: 0.03 parts, surfactant (polyoxyethylene lauryl) Ether, Emalex 710, manufactured by Nippon Emulsion Co., Ltd.) 1% by weight aqueous solution: 0.86 parts, ion-exchanged water: 6.0 parts

  A method for preparing the inorganic layered compound dispersion (1) used in the protective layer coating solution is shown below.

<Preparation of inorganic layered compound dispersion (1)>
6.4 parts of synthetic mica (Somasif ME-100, manufactured by Coop Chemical Co., Ltd.) was added to 193.6 parts of ion-exchanged water, and dispersed using an homogenizer until the average particle size (laser scattering method) became 3 μm. . The aspect ratio of the obtained dispersed particles was 100 or more.

2. Production of lithographic printing plate precursor B In the production of the lithographic printing plate precursor A, the preparation for Examples 9 to 33 and Comparative Examples 5 to 14 was carried out in the same manner as the production of the lithographic printing plate precursor A except that a protective layer was not applied. A lithographic printing plate precursor B was prepared.
Tables 2 and 3 summarize the support used in the preparation of each lithographic printing plate precursor, the compound represented by Formula 1 in the image recording layer coating solution (1), or the comparative compound.

3. Evaluation of lithographic printing plate precursor The above-described lithographic printing plate precursors were evaluated for color developability, on-press developability, printing durability and stability over time as follows. The evaluation results are shown in Tables 1 to 3.

(1) Color development The lithographic printing plate precursor was output by using a Trend setter 3244VX manufactured by Creo with a water-cooled 40 W infrared semiconductor laser, an output of 11.5 W, an outer drum rotation speed of 220 rpm, and a resolution of 2,400 dpi (dot per inch, 1 inch = 25.4 mm). ). The exposure was performed in an environment of 25 ° C. and 50% RH.
The color development of the lithographic printing plate precursor was measured immediately after exposure and after storage for 2 hours in a dark place (25 ° C.) after exposure. The measurement was performed by a SCE (regular reflection light removal) method using a spectrocolorimeter CM2600d manufactured by Konica Minolta Co., Ltd. and operation software CM-S100W. The color developability was evaluated by the difference ΔL between the L ^* value of the exposed area and the L ^* value of the unexposed area using the L ^* value (brightness) of the L ^* a ^* b ^* color system. The larger the value of ΔL, the better the color developability.

(2) On-machine developability The lithographic printing plate precursor was exposed under conditions of an external drum rotation speed of 750 rpm, a laser output of 70%, and a resolution of 2,400 dpi using Fujifilm Corporation's Luxel PLASETTER T-6000III equipped with an infrared semiconductor laser. . The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The exposed lithographic printing plate precursor was mounted on the plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Equality-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) dampening water and Values-G (N) black ink (manufactured by DIC Graphics Co., Ltd.) Dampening water and ink were supplied by the standard automatic printing start method, and 100 sheets were printed on Tokishi Art Paper (76.5 kg) (Mitsubishi Paper Co., Ltd.) at a printing speed of 10,000 sheets per hour. .
The on-machine development of the unexposed part of the image recording layer on the printing machine was completed, and the number of printing sheets required until the ink was not transferred to the non-image part was measured and evaluated as on-machine developability. The smaller the number, the better the on-press developability.

(3) Printing durability with respect to oil-based ink After the on-press developability was evaluated, printing was further continued. As the number of printed sheets increased, the image recording layer gradually worn out, so that the ink density on the printed material decreased. The number of printed sheets was measured until the dot area ratio of 50% halftone dots of FM screen in the printed matter was measured by a Gretag densitometer (manufactured by GretagMacbeth) was 5% lower than the measured value of the 100th printed sheet. Evaluation was made based on the relative printing durability when the number of printed sheets was 50,000. The larger the value, the better the printing durability.
Relative printing durability = (number of printed target lithographic printing plate precursors) / 50,000 × 100

(4) Printing durability against ultraviolet curable ink (UV ink) An external drum rotation speed of 750 rpm, laser output of 70%, resolution with a FUJIFILM Luxel PLANETTER T-6000III equipped with an infrared semiconductor laser. The exposure was performed at 2,400 dpi. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed original plate was attached to a cylinder of Heidelberg printing machine SX-74 having a chrysanthemum size (636 mm × 939 mm) without developing. A 100 L dampening water circulation tank containing a nonwoven fabric filter and a temperature control device was connected to the printing press. Dampening water S-Z1 (Fuji Film Co., Ltd.) 2.0% dampening water 80L is charged into the circulation device, and T & K UV OFS K-HS black ink GE-M (manufactured by T & K TOKA Co., Ltd.) is used as printing ink. ), And dampening water and ink were supplied by a standard automatic printing start method, and then printed on Tokishi Art (76.5 kg) paper at a printing speed of 10,000 sheets per hour.
As the number of printed sheets increased, the image recording layer gradually worn out, so that the ink density on the printed material decreased. The number of printed sheets was measured until the value obtained by measuring the dot area ratio of the 50% halftone dot of the FM screen in the printed matter with a Gretag densitometer was 5% lower than the measured value of the 100th printed sheet. Evaluation was made based on the relative printing durability when the number of printed sheets was 50,000. The larger the value, the better the printing durability.
Relative printing durability = (number of target lithographic printing plate precursors printed) / 50,000 × 100

(5) Stability over time The image recording layer coating solution (1) used for the preparation of the lithographic printing plate precursors A and B is heated at 60 ° C. for 1 day, and the residual ratio of the compound represented by Formula 1 or the comparative compound Was measured by high performance liquid chromatography (HPLC). Moreover, a lithographic printing plate precursor was prepared using a coating solution heated at 60 ° C. for 1 day, and the stability over time was evaluated.
In the following table, ΔE represents the difference between the HOMO orbital energy level of the compound represented by Formula 1 or the comparative compound used and the HOMO orbital energy level of the electron-donating polymerization initiator.

  From the results described in Tables 1 to 3, the lithographic printing plate precursors according to the present disclosure of Examples 1 to 33 are all good in printing durability, color developability, on-press development property, and stability over time. On the other hand, it can be seen that the lithographic printing plate precursor of Comparative Example is inferior in at least one of printing durability and color developability.

The disclosure of Japanese Patent Application No. 2017-137249 filed on July 13, 2017 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described in this specification are the same as if each document, patent application, and technical standard were specifically and individually stated to be incorporated by reference. Which is incorporated herein by reference.

Claims (12)

Having an image recording layer on a hydrophilic support;
The image recording layer contains a polymerization initiator, an infrared absorber, a polymerizable compound, and an acid color former,
The polymerization initiator includes an electron donating polymerization initiator,
The infrared absorber includes a compound represented by the following formula 1,
A lithographic printing plate precursor wherein the difference between the HOMO of the compound represented by Formula 1 and the HOMO of at least one of the electron donating polymerization initiators is 0.60 eV or less.

R ₁ and R ₂ each independently represents a hydrogen atom or an alkyl group, R ₁ and R ₂ may be linked to each other to form a ring, and R _{3 to} R ₆ are each independently a hydrogen atom or an alkyl group. R ₇ and R ₈ each independently represents an alkyl group or an aryl group, Y ₁ and Y ₂ each independently represent an oxygen atom, a sulfur atom, —NR ₀ — or a dialkylmethylene group, Ar ₁ and Ar ₂ each independently represent a group which forms a benzene ring or a naphthalene ring which may have -X described later, and A ₁ represents -NR ₉ R ₁₀ , -X ₁ -L ₁ or described later. represents -X to each R ₉ and R ₁₀ are independently an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, X ₁ is an oxygen atom or a sulfur atom, L ₁ represents a hydrocarbon , Heteroaryl group, or represents a bond cleaves group of X ₁ by the heat or infrared exposure, Za represents a counter ion for neutralizing the electric charge, at least one of Ar ₁ and Ar _2, by the following formula 2 Having the group represented.
85
-X Formula 2
X is a halogen atom, —C (═O) —X ₂ —R ₁₁ , —C (═O) —NR ₁₂ R ₁₃ , —O—C (═O) —R ₁₄ , —CN, —SO ₂ NR ₁₅ R ₁₆ or a perfluoroalkyl group, X ₂ represents a single bond or an oxygen atom, R ₁₁ and R ₁₄ each independently represents an alkyl group or an aryl group, R ₁₂ , R ₁₃ , R ₁₅ and R ₁₆ each independently represents a hydrogen atom, an alkyl group or an aryl group. The lithographic printing plate precursor as claimed in claim 1, wherein X in the formula 2 is a fluorine atom, a chlorine atom, or —C (═O) OR ₁₇ . The lithographic printing plate precursor as claimed in claim 2 , wherein in Formula 1, A ₁ is —NR ₁₈ R ₁₉ or —S—R ₂₀ .
R ₁₈ and R ₁₉ each independently represents an aryl group, and R ₂₀ represents a hydrocarbon group or a heteroaryl group. The lithographic printing plate precursor according to any one of claims 1 to 3 , wherein the electron-donating polymerization initiator is a borate compound. The lithographic printing plate precursor as claimed in claim 4 , wherein the borate compound is a tetraarylborate compound or a monoalkyltriarylborate compound. The lithographic printing plate precursor as claimed in any one of claims 1 to 5 , wherein the polymerization initiator further comprises an electron-accepting polymerization initiator. The said acid color former is at least 1 sort (s) of compounds chosen from the group which consists of a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound, The any one of Claims 1-6. Lithographic printing plate precursor. The lithographic printing plate precursor as claimed in any one of claims 1 to 7 , wherein Za is an organic anion containing a carbon atom. The lithographic printing plate precursor according to any one of claims 1 to 8 , wherein Za is a sulfonimide anion. The lithographic printing plate precursor as claimed in any one of claims 1 to 9 , wherein the polymerizable compound comprises a urethane-based addition polymerizable compound. The polymerizable compound includes at least one compound selected from the group consisting of esters of unsaturated carboxylic acids and polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and polyvalent amine compounds. Item 11. The lithographic printing plate precursor according to any one of Items 1 to 10 . A step of exposing the lithographic printing plate precursor according to any one of claims 1 to 11 imagewise to form an exposed portion and an unexposed portion; and
A method for producing a lithographic printing plate comprising a step of supplying at least one of printing ink and fountain solution to remove the unexposed portion.